Fake news was the word of the year for 2017, we are often bombarded by information and it can be very difficult to fact check. Sometimes we just don’t have time to check the information we are given is correct, and other times we are relying on the credential of the writer. The aquarium hobby is no exception with so many different websites and social media platforms all arguing for space and more importantly your trust.
As distrust in authority increases there has never been so much division and this leads into the influences of certain media. Unlike the general hobby there is a strong influence of science, whether the website is actually scientific or not.
This is best discussed in terms of two of the biggest myths that have arisen in the last few years.
How Epistylis ruled the world.
For many years the protozoan whitespot, Ichthyophthirius multifiliis was widely considered the most common parasite on fishes, it is well studied in the scientific literature (Francis-Floyd et al., 2016, 2023) followed by velvet, Oodinium and Piscinoodiniasis. Disease is tricky, unlike identifying animals we don’t necessary have the tools as a hobby for an accurate diagnosis, there are thousands of species to separate.
Realistically these two pathogens are one of many that can appear as spots on the fishes body, generally most treatments will cover them. Although there is suggestion that the formalin based treatments are less effective as I discuss here, maybe this has lead to why people come to think they are not dealing with white spot? Because shouldn’t white spot treatments work for I. multifiliis? In addition there is proven acquired immunity to I. multifiliis (Teixeira Alves and Taylor, 2020) but it doesn’t mean that it is unseen. In fact I have noticed a reduced number personally and online of those spotted parasitic cysts, but that is just experience. To add to the confusion not all of these parasites do appear as spots (Sudhagar et al., 2022; Fig 1). I. multifilliis and Piscinoodiniasis is known to target the gills of fishes.
An infection of Piscinoodinium as featured in: Sudhagar, A., Sundar Raj, N., Mohandas, S. P., Serin, S., Sibi, K. K., Sanil, N. K., & Raja Swaminathan, T. (2022). Outbreak of Parasitic Dinoflagellate Piscinoodinium sp. Infection in an Endangered Fish from India: Arulius Barb (Dawkinsia arulius). Pathogens, 11(11), 1350.
This confusion isn’t aided by nematode cysts looking incredibly similar to I. multifilliis and that used to be quite a common misdiagnosis. Going back to the difficulties in identification, microscopes are very important here as many of these pathogens are really only different to look at under the microscope. Using a microscope is one thing but identifying what you are looking at is another, the koi world seems to have this sorted with pathologists available but it seems to have been a reduced talent within the aquarium hobby. There are very few useful books on pathology still available, most if all will be second hand. Microscopes are really only useful for what can be seen so bacteria and even more viruses are another ball game, requiring expensive technology to identify the pathogen.
So, the story is set for Epistylis. Why Epistylis? We will never know but it is likely a random page that came up and sometimes names stick. Unlike Ichthyophthirius multifiliis, Epistylis is easy to remember. I don’t think the why matters but more that it is there, it’s difficult to work out what website started it.
Figure 2: Whitespot, Ichthyophthirius multifiliis as featured in: Martins, M. L., Cardoso, L., Marchiori, N., & Benites de Pádua, S. (2015). Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Revista Brasileira de Parasitologia Veterinária, 24, 1-20.
It might be that fact checking takes time and we should trust what we read to be true. but Ichthyophthirius multifiliis looks nothing alike Epistylis in any way that can be confused as you can clearly see in figure 2 and 3.
Figure 3: Epistylis as featured in: Martins, M. L., Cardoso, L., Marchiori, N., & Benites de Pádua, S. (2015). Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Revista Brasileira de Parasitologia Veterinária, 24, 1-20.
What is more clear is that Epistylis is almost always present and not always as a pathogen, it can also be asymptomatic (Ksepka et al., 2021). But if symptomatic it is expressed as more of a plaque that could be confused with some of the herpes viruses (Fig 3).
So why are they confused? It has to do with this graph (Fig 4). Firstly ich is referring to Ichthyophthirius multifiliis, that we more then often call whitespot in the UK. No citations are provided so this is not backed up with the identification of Epistylis. So some will say the science is wrong, the issue is that genera are described with set features and if those features don’t match then that is not that species, it would be another. That’s how scientific descriptions work. Epistylis doesn’t display itself as distinct round spots whether rough sized or not (Ksepka et al., 2021; Wu et al., 2021; Valladao et al., 2015). If it was so common and lethal there would be more literature when in reality there isn’t that much comparatively. In my experience as well white spot can kill a fish rapidly, and due to the effect on the gills it is quite taxing on the fish (Martins et al., 2015).
So why this whole essay? To discuss misinformation I must first state why this myth isn’t true. Interestingly it is a brilliant story regarding understanding critical analysis.
How to identify a reliable website:
Ability to cite their sources, ideally papers if they are scientists.
Using standard length, just because there are no reliable measurements of total size including the caudal/tail fin.
Avoiding plagiarism, if a scientist this is a key issue.
References:
Francis-Floyd, R., Yanong, R., & Pouder, D. (2023). Ichthyophthirius multifiliis (white spot) infections in fish.
Francis-Floyd, R., Yanong, R., & Pouder, D. (2016). Ichthyophthirius multifiliis (White Spot) Infections in Fish: CIR920/FA006, rev. 12/2016. EDIS, 2016(10).
Ksepka, S. P., & Bullard, S. A. (2021). Morphology, phylogenetics and pathology of “red sore disease”(coinfection by Epistylis cf. wuhanensis and Aeromonas hydrophila) on sportfishes from reservoirs in the South‐Eastern United States. Journal of Fish Diseases, 44(5), 541-551.
Martins, M. L., Cardoso, L., Marchiori, N., & Benites de Pádua, S. (2015). Protozoan infections in farmed fish from Brazil: diagnosis and pathogenesis. Revista Brasileira de Parasitologia Veterinária, 24, 1-20.
Sudhagar, A., Sundar Raj, N., Mohandas, S. P., Serin, S., Sibi, K. K., Sanil, N. K., & Raja Swaminathan, T. (2022). Outbreak of Parasitic Dinoflagellate Piscinoodinium sp. Infection in an Endangered Fish from India: Arulius Barb (Dawkinsia arulius). Pathogens, 11(11), 1350.
Teixeira Alves, M., & Taylor, N. G. (2020). Models suggest pathogen risks to wild fish can be mitigated by acquired immunity in freshwater aquaculture systems. Scientific Reports, 10(1), 7513.
Valladao, G. M. R., Levy-Pereira, N., Viadanna, P. H. D. O., Gallani, S. U., Farias, T. H. V., & Pilarski, F. (2015). Haematology and histopathology of Nile tilapia parasitised by Epistylis sp., an emerging pathogen in South America. Bulletin of the European Association of Fish Pathologists, 35(1), 14-20.
Wang, Z., Zhou, T., Guo, Q., & Gu, Z. (2017). Description of a new freshwater ciliate Epistylis wuhanensis n. sp.(Ciliophora, Peritrichia) from China, with a focus on phylogenetic relationships within family Epistylididae. Journal of Eukaryotic Microbiology, 64(3), 394-406.
Wu, T., Li, Y., Zhang, T., Hou, J., Mu, C., Warren, A., & Lu, B. (2021). Morphology and molecular phylogeny of three Epistylis species found in freshwater habitats in China, including the description of E. foissneri n. sp.(Ciliophora, Peritrichia). European Journal of Protistology, 78, 125767.
Loricariidae, also known under the common names L numbers, whiptail catfishes and pleco’s are popular fishes within the aquarium trade. Many people will come across the problem in their new fish where they will not eat and in fact they might never eat.
Worming
The first sign might be that the fish might have a concaved stomach and the first solution will be to worm the fish. I doubt this is the usual cause of the concave stomach in Loricariid’s but it is worth crossing out, Loricariids do quite frequently have parasitic worm’s (usually nematodes rather then Annelid’s) in the wild and these will maintain at a low level (Borges et al., 2018). If a fish is stressed such as from import this parasite load can become much higher then a healthy level. So there is logic in worming fishes when they arrive and most stores do this. Most wormers cover different internal parasites but the most common would be containing praziquantel, levamisole and flubendazole (do not use with stingrays). I would personally advise definitely not using more then one as they do all have side effects. Generally wormers need to be repeated after a week to cover the parasites lifecycle.
Panaqolus aff. maccus
The importance of getting the fish feeding.
While a rounded and healthy diet is important for wild caught fishes particularly they do need to feed. It is quite a large jump for many from a wild diet to a captive diet and many might not even identify it as food.
More importantly it is possible that the gut flora, microbes will start to decline in number while they are not eating and for shipping this is useful but not for keeping the fish. One possible thing that could help this is rather then adding them to a clean quarantine tank is to one where other similar species have lived, there is likely a benefit from those fishes waste in rebuilding that gut flora lost after shipping.
What should I feed my fish?
First identify what they eat, so their natural diet. While most diets contain the steryotypical fish/insect/krill meal, cereal, vegetable and minimal algae diets this is no issue in the short term but many wont touch these diets at first. So regardless of long term them being vastly different from their natural diet and homogenous whether you have a Trophius, Loricariid or angelfish they actually are the same (Vucko et al., 2017); they can also be unhelpful.
This is important as feeding an incorrect diet can lead to bloat and other issues, it has been commonly noted when Hypancistrus are fed a wholly carnivorous diet.
Carnivorous species
This is only for true carnivores but aspects of this can be fed to others in small numbers with care, avoid it with some of the more extreme algivores such as Ancistrus, Chaetostoma, Baryancistrus etc.
Mussels and prawns are very good for getting a fish feeding at first but the issue with these two food items at high in thiaminase and therefore degrade thiamin, vitamin b1.
Generally for this reason I’d advise a range of frozen foods and for some larger species earthworms might not be a bad choice.
Nannopotopoma sp. ‘Peru/robocop’ at Maidenhead Aquatics at Ascot
Algivores and Detritivores
This includes most Loricariids that people keep to some degree but the specialities within their diet are best looking at later.
These are definitely the most tricky to get feeding at first and I often give a range of options even at the same time. Generally I’d offer that dry/gel diet once or twice a day and vegetables replaced every 12-24 hours depending on how quickly they are braking down.
For dry/gel diets I’d offer certainly Repashy soilent green if possible as I’ve never had a fish fail to give it a go. Later on I’d bulk it out with other ingredients such as algal powders, you could do similar with other gel diets but I can’t say fishes are going to take up them as well. At the end of the day whatever they are eating in the short term is worth it. Remember vegetables and similar are more treats as do not even closely replicate their wild diets.
Vegetables and other easy food items you can leave in for the fishes:
Courgette
Reasonable in nutrition, is willingly eaten by many fishes but they might select either the flesh or skin over the other.
Cucumber
While often declared as low nutrients due to water content they do contain minerals and other compounds that have nutritional value.
Mushrooms (Edible species from supermarket)
Could be part of a staple diet for Panaqolus, Panaque and Hypostomus cochliodon group as they do feed on fungi in the wild (Lujan et al., 2011). It is difficult to say the nutrition levels for these fishes as many might be able to digest more so then nutritional estimates for humans. So far mushrooms are shown to increase weight gain opposed to traditional diets (Zakaria et al., 2021; Dawood et al., 2010), a potential prebiotic (Chandra & Qureshi, 2023) and other potential benefits (Sánchez-Velázquez et al., 2014)
Sweet Potatoes
These doesn’t need to be blanched and I am not convinced by their digestibility for Loricariids (Omoregie et al., 2009) but if they can get the fish feeding that is what matters.
Further on I find whether fishes feed on these more hit and miss.
Green beans
The common bristlenose, Ancistrus sp. is meant to be a big fan of this. Nutrition doesn’t need to be debated but as a plant would be more of a treat after acclimation.
Bell peppers
I don’t think it entirely matters whether the pepper is red, yellow or green but the sugar and nutrition levels will vary.
Pumpkins and other squashes
I find very hit or miss but never blanched them. They can break down very quickly producing a film over the fruit. I would say they are much more similar to courgette.
Later on and narrowing down the diet
While whatever they will eat is generally the best rule as they are acclimatizing over the first few weeks and months. Afterwards I would look to narrowing down their diet to what they would feed on in the wild as in the articles mentioned earlier on.
Is the setup right?
This sometimes get’s forgotten but a major part of why a fish might not be feeding could be they are not getting to the food. Loricariids are slow to feed, some might take hours even without lights to feed and this can make some tankmates ill-suited. Some tankmates might work better where if needed you can remove them to another tank so that is worth considering particularly for many cichlids, many shoaling species in very high numbers or quite a few live numbers.
Planiloricaria cryptodon at Maidenhead Aquatics at Ascot.
References:
Borges, W. F., de Oliveira, M. S. B., Santos, G. G., & Tavares-Dias, M. (2018). Parasites in Loricariidae from Brazil: checklist and new records for fish from the Brazilian Amazon. Acta Scientiarum. Biological Sciences, 40, 1-9.
Chandra, O. P., & Qureshi, Y. (2023). Importance of mushroom supplementation as a prebiotic amalgamation in fed diet of improvement of weight gain (WG) in Nile Tilapia,(Oreochromis niloticus). Journal of Pharmaceutical Negative Results, 1681-1687.
Dawood, M. A., Eweedah, N. M., El-Sharawy, M. E., Awad, S. S., Van Doan, H., & Paray, B. A. (2020). Dietary white button mushroom improved the growth, immunity, antioxidative status and resistance against heat stress in Nile tilapia (Oreochromis niloticus). Aquaculture, 523, 735229.
Lujan, N. K., German, D. P., & Winemiller, K. O. (2011). Do wood‐grazing fishes partition their niche?: morphological and isotopic evidence for trophic segregation in Neotropical Loricariidae. Functional Ecology, 25(6), 1327-1338.
Omoregie, E., Igoche, L., Ojobe, T. O., Absalom, K. V., & Onusiriuka, B. C. (2009). Effect of varying levels of sweet potato (Ipomea Batatas) peels on growth, feed utilization and some biochemical responses of the cichlid (Oreochromis Niloticus). African Journal of Food, Agriculture, Nutrition and Development, 9(2), 700-712.
Sánchez-Velázquez, J., Peña-Herrejón, G. A., & Aguirre-Becerra, H. (2024). Fish Responses to Alternative Feeding Ingredients under Abiotic Chronic Stress. Animals, 14(5), 765.
Vucko, M. J., Cole, A. J., Moorhead, J. A., Pit, J., & de Nys, R. (2017). The freshwater macroalga Oedogonium intermedium can meet the nutritional requirements of the herbivorous fish Ancistrus cirrhosus. Algal research, 27, 21-31.
Zakaria, Z., Abd Rasib, N. A., & Tompang, M. F. (2021). Spent mushroom substrate based fish feed affects the growth of catfish (Clarias gariepinus). In IOP Conference Series: Earth and Environmental Science (Vol. 765, No. 1, p. 012082). IOP Publishing.
Corydoras is a genus of Catfishes in the family Callichthyidae. Callichthyidae includes: Callichthyinae (Callichthys, Lepthoplosternum, Hoplosternum, Megalechis and Dianema); Corydoralinae which is the focus of this article and revision. Figure 1 explains the topography (family tree format) of this group but bare in mind it doesn’t reflect the current knowledge for Corydoralinae.
Figure 1: Phylogeny of Callichthyidae. Bare in mind the topography (shape) of Corydoras doesn’t match our current understanding. As featured in: Shimabukuro-Dias, C. K., Oliveira, C., Reis, R. E., & Foresti, F. (2004). Molecular phylogeny of the armored catfish family Callichthyidae (Ostariophysi, Siluriformes). Molecular Phylogenetics and Evolution, 32(1), 152-163.
Previously many genera were inferred for members of what was known for a long time as Corydoras but over time these were synonymized finalizing with Britto (2003) which resulted in Brochis no longer being valid. To put it simply as there were many reasons behind but also to have Corydoras as the genus it was then Brochis would have to be Corydoras.
Figure 2: Phylogeny of Corydoralinae featured in: Alexandrou, M. A., Oliveira, C., Maillard, M., McGill, R. A., Newton, J., Creer, S., & Taylor, M. I. (2011). Competition and phylogeny determine community structure in Müllerian co-mimics. Nature, 469(7328), 84-88.
The history is a bit messy. We have known for a long time Corydoras has had a lineage system, this was explained clearly in Alexandrou et al (2011). This phylogeny shows how embedded Brochis is inside of Corydoras and therefore would not easily be valid as a genus.
The issue of type species
So while many of the ‘Corydoras‘ kept in the aquarium trade are not Corydoras, the type, C. geoffroy places in lineage 1. These would be the only true Corydoras, basically this is the reference species in a way.
Some might note what was known as Aspidoradini, a tribe separate to what was Corydoras branches out in the middle of Corydoras, more problems. It’s really messy.
What are the new genera?
Corydoras: Used to represent lineage 1 of Corydoras. These have a but curved block shaped head, most distinctively is a filament behind the barbel’s which can look like an additional barbel.
Aspidoras: Always known as Aspidoras but excludes Gastrodermis pauciradiatus.
Scleromystax: Sometimes known as bearded Corydoras, the only to show really clear sexual dimorphism through odontodes.
Gastrodermus: Originally the C. elegans group, lineage 5 and the microcorydoras such as G. pygmeaus and G. hastatus. Much shorter and rounder in the head but still slightly trinagular unlike Hoplisoma.
Osteogaster: Originally the C. aeneus group, contains the bronze, O. aeneus. Rounded head, short.
Brochis: This is a much larger group, likely for the time being. Contains the whole of lineage 8 from what was Brochis to species such as C. arcuatus. Similar to Corydoras the majority have large heads but these lack the curvature of Corydoras, similarly contains many large members.
Hoplisoma: Lineage 9, another very popular genus from the trade. Very rounded head but much shorter then Osteogaster.
Corydoradinae head shapes
The clearest way to see the difference between the different genera is their head shapes, there is quite the diversity as shown in the above figure. The majority of these genera can be identified from that head shape in my opinion. Brochis seems to display the widest range of morphological disparity in head shape but this can be expected from such a large genus.
Why is this revision important?
This revision reflects our current knowledge of the group Corydoradinae, both regarding morphological and molecular information. Rather then have one large category which doesn’t describe the morphological diversity or any phylogenetic information, these genera are easier to navigate particularly for a hobbyist. Not just does their morphology differ but likely their care. I already know Corydoras and some Brochis display territorial behavior which is not reflective of all groups, from a hobbyist view point knowing the genera helps avoid this, or avoid larger species.
Revisions are normal in science as technology and knowledge advances, they aren’t done for no reason or for publication. Over time we have developed techniques that have helped us understand the evolution of fishes better and therefore give them more accurate names that reflect this evolution. Technology such as Computerized tomography (CT) scanning, extracting DNA from formalin preserved/historical specimens, gene expression, developmental techniques etc. We can now understand fishes in a way we never could before, it means that change is inevitable but it’s the path to understanding evolution, biodiversity and reflecting that in how we name species, genera, families etc.
This work was done by the scientists; Angelica C. Dias, Luiz F. C. Tencatt, Fabio F. Roxo, Gabriel de Souza da Costa Silva, Sérgio A. Santos, Marcelo R. Britto, Dr. Martin I. Taylor and Dr. Claudio Oliveira.
No doubt our knowledge of Corydoradinae wouldn’t be the same without the efforts of Steven Grant (Catfishes of the World) and Ian Fuller who runs Corydoras World, both have done a lot for bridging the gap between the hobbyist and the scientist. Corydoras World I can certainly recommend for anyone who wants to learn more about this curious group of fishes.
What species are what?
To save time I wont cite authors, but this should ideally be done. I wont include C and CW numbers as it’ll make the lists much much longer.
Corydoras
Corydoras acutus
Corydoras amapaensis
Corydoras areio
Corydoras aurofrenatus
Corydoras blochi
Corydoras caramater
Corydoras cervinus
Corydoras coriatae
Corydoras cortesi
Corydoras desana
Corydoras filamentosus
Corydoras fowleri
Corydoras fulleri
Corydoras geoffroy
Corydoras maculifer
Corydoras narcissus
Corydoras negro
Corydoras ourastigma
Corydoras oxyrhynchus
Corydoras pastazensis
Corydoras saramaccensis
Corydoras sarareensis
Corydoras semiaquilus
Corydoras septentrionalis
Corydoras serratus
Corydoras simulatus
Corydoras solox
Corydoras spilurus
Corydoras stenocephalus
Corydoras treitlii
Corydoras vittatus
Corydoras zawadzkii
Aspidoras
Aspidoras albater
Aspidoras aldebaran
Aspidoras azaghal
Aspidoras belenos
Aspidoras brunneus
Aspidoras carvalhoi
Aspidoras depinnai
Aspidoras fuscoguttatus
Aspidoras gabrieli
Aspidoras kiriri
Aspidoras lakoi
Aspidoras maculosus
Aspidoras mephisto
Aspidoras poecilus
Aspidoras psammatides
Aspidoras raimundi
Aspidoras rochai
Aspidoras velites
Scleromystax
Scleromystax barbatus
Corydoras lacerdai
Scleromystax macropterus
Scleromystax prionotos
Scleromystax reisi
Scleromystax salmacis
Scleromystax virgulatus
Gastrodermus
Gastrodermus bilineatus
Gastrodermus elegans
Gastrodermus gracilis
Gastrodermus guapore
Gastrodermus hastatus
Gastrodermus latus
Gastrodermus mamore
Gastrodermus nanus
Gastrodermus napoensis
Gastrodermus nijsseni
Gastrodermus paucerna
Gastrodermus pauciradiatus
Gastrodermus pygmaeus
Gastrodermus undulatus
Osteogaster
Osteogaster aeneus
Osteogaster eques
Osteogaster hephaestus
Osteogaster maclurei
Osteogaster melanotaenia
Osteogaster rabauti
Osteogaster zygatus
Brochis
Brochis agassizii
Brochis amandajanea
Brochis ambiacus
Brochis approuaguensis
Brochis arcuatus
Brochis bethanae
Brochis bifasciatus
Brochis britskii
Brochis brittoi
Brochis condiscipulus
Brochis costai
Brochis crimmeni
Brochis crypticus
Brochis delphax
Brochis deweyeri
Brochis difluviatilis
Brochis ephippifer
Brochis garbei
Brochis geryi
Brochis gomezi
Brochis haraldschultzi
Brochis heteromorphus
Brochis imitator
Brochis incolicana
Brochis isbrueckeri
Brochis lamberti
Brochis leopardus
Brochis multiradiatus
Brochis noelkempffi
Brochis ornatus
Brochis orphnopterus
Brochis pantanalensis
Brochis pinheiroi
Brochis pulcher
Brochis reticulatus
Brochis robineae
Brochis robustus
Brochis seussi
Brochis sodalis
Brochis spectabilis
Brochis splendens
Brochis sychri
Brochis virginiae
Hoplisoma
Hoplisoma acrensis
Hoplisoma adolfoi
Hoplisoma albolineatum
Hoplisoma amphibelum
Hoplisoma apiaka
Hoplisoma araguaiaensis
Hoplisoma armatum
Hoplisoma atropersonatum
Hoplisoma axelrodi
Hoplisoma baderi
Hoplisoma benattii
Hoplisoma bicolor
Hoplisoma boehlkei
Hoplisoma boesemani
Hoplisoma bondi
Hoplisoma breei
Hoplisoma brevirostris
Hoplisoma burgessi
Hoplisoma carlae
Hoplisoma caudimaculatum
Hoplisoma cochui
Hoplisoma colossus
Hoplisoma concolor
Hoplisoma copei
Hoplisoma coppenamensis
Hoplisoma cruziensis
Hoplisoma davidsandsi
Hoplisoma diphyes
Hoplisoma duplicareum
Hoplisoma ehrhardti
Hoplisoma esperanzae
Hoplisoma evelynae
Hoplisoma eversi
Hoplisoma flaveolum
Hoplisoma froehlichi
Hoplisoma gladysae
Hoplisoma gossei
Hoplisoma granti
Hoplisoma griseum
Hoplisoma gryphus
Hoplisoma guianensis
Hoplisoma habrosum
Hoplisoma julii
Hoplisoma kanei
Hoplisoma knaacki
Hoplisoma lacrimostigmata
Hoplisoma leucomelas
Hoplisoma longipinnis
Hoplisoma loretoensis
Hoplisoma loxozonum
Hoplisoma lymnades
Hoplisoma melanistium
Hoplisoma melini
Hoplisoma metae
Hoplisoma micracanthus
Hoplisoma microcephalum
Hoplisoma multimaculatum
Hoplisoma nattereri
Hoplisoma oiapoquensis
Hoplisoma ortegai
Hoplisoma osteocarum
Hoplisoma paleatus
Hoplisoma panda
Hoplisoma paragua
Hoplisoma parallelum
Hoplisoma pavanelliae
Hoplisoma petracinii
Hoplisoma polystictum
Hoplisoma potaroensis
Hoplisoma punctatum
Hoplisoma revelatum
Hoplisoma reynoldsi
Hoplisoma sanchesi
Hoplisoma schwartzi
Hoplisoma similis
Hoplisoma sipaliwini
Hoplisoma steindachneri
Hoplisoma sterbai
Hoplisoma surinamensis
Hoplisoma trilineatum
Hoplisoma tukano
Hoplisoma urucu
Hoplisoma weitzmani
Hoplisoma xinguensis
References:
Alexandrou, M. A., Oliveira, C., Maillard, M., McGill, R. A., Newton, J., Creer, S., & Taylor, M. I. (2011). Competition and phylogeny determine community structure in Müllerian co-mimics. Nature, 469(7328), 84-88.
Britto, M. R. (2003). Phylogeny of the subfamily Corydoradinae Hoedeman, 1952 (Siluriformes: Callichthyidae), with a definition of its genera. Proceedings of the Academy of Natural Sciences of Philadelphia, 153(1), 119-154.
Dias, A. C., Tencatt, L. F., Roxo, F. F., Silva, G. D. S. D. C., Santos, S. A., Britto, M. R., … & Oliveira, C. (2024). Phylogenomic analyses in the complex Neotropical subfamily Corydoradinae (Siluriformes: Callichthyidae) with a new classification based on morphological and molecular data. Zoological Journal of the Linnean Society, zlae053.
Shimabukuro-Dias, C. K., Oliveira, C., Reis, R. E., & Foresti, F. (2004). Molecular phylogeny of the armored catfish family Callichthyidae (Ostariophysi, Siluriformes). Molecular Phylogenetics and Evolution, 32(1), 152-163.
Little seems known about the diet of Corydoradinae, it might be due to a generalization of the genus but also a lack of understanding of their ecology. For scientists it is a relatively small genus from a small family, Callichthyidae which also contains genera such as Megalechis, Hoplosternum and Aspidoras.
Brochis bethanae CW006 also known as the Narcisso Corydoras taken at Maidenhead Aquatics, Ascot
There is no doubt that Corydoras feeds largely as a carnivore but as a term that is very vague. These fishes are hardly hunting down capybara that enter the water or swarming round the carcasses of fishes. Carnivory purely just refers to the fact an animal eats an animal, and what is defined as an animal is just Animalia which is a gigantic category of organisms. Animalia covers from the simple sponges and corals all the way to molluscs, mammals and fishes, it includes some strange organisms as well like bryozoa and jellyfish. Each of these animals will have different nutritional compositions, some toxins but also accessibility. It is well known that insectivores (carnivores that specialize on insects) are not able to access nutrition from fishes, mammals etc. efficiently (Žák et al., 2022), this also increases nitrogenous waste. There might be other aspects of nutrition commonly missed such as perhaps the importance of chitin? It’s very difficult to digest, too much and the food item wont be processed, too little might result in blockages. It reminds me very much of the bloodworm used in the aquarium trade having a strong chitin casing compared to the chromatid larvae the fishes are likely eating in the wild. I have seen bloodworm pass out the fish as if it hadn’t been eaten at all, even carnivorous fishes. Not just does carnivory cover a wide range of different nutritional profiles and species but also modes of feeding. It is very different to catch and feed on a whole fish as it is to maybe feed on scales (lepidophagy), break down snails (durophagy), maybe extract a snail from it’s shell etc. Carnivory is so obviously diverse compared to herbivory but it still is best visualized like a field of grass, all grass specialists but put sheep, cattle and horses out and they will all feed on very different parts of the grass.
What I am emphasizing is not to generalize any dietary category and just fall to the general diets for fishes. Carnivory is just a man made category regardless and doesn’t reflect realistically aquatic dietary niches.
Corydoradinae has previously been identified as an omnivore by Nijssen (1970) although only used aquarium fishes as evidence. This paper records them feeding on fallen leaves of which I find particularly strange. Although a particular fondness for invertebrates is noted, particularly tubifex and daphina, identifying the worms using their highly evolved sense of smell/taste. This record is later referenced in Alexandrou et al. (2011) but also noted that they feed on algae, insects, zooplankton and annelids. Algae I would not be surprised that is consumed but I do not believe they are targeting it, much like invertebrates are found in small numbers the guts of grazing Loricariids.
Isotope analysis was used to compare different lineages of Corydoras and identify any partitioning in where and what they feed on. Different lineages display divergent nutritional profiles between different genera of Corydoradinae based on head shape, eye placement and body depth. There is a clear difference between the diet of the longer snouted and shorter snouted Hoplisoma and Gastrodermus, I can assume due to the depths of substrate that can be exploited by either. These longer snouted, Corydoras are referenced as feeding on a lower trophic level (Alexandrou et al., 2011). This could infer on feeding on more algaes but maybe those lower trophic level invertebrates such as worms who would be lower down in the substrate then predatory invertebrates.
The shorter to medium snouted Hoplisoma paleatum, the peppered ‘Corydoras‘ is recorded as feeding largely on fly larvae such as chromatid’s with a small addition of nematode’s. Algae and plant fragments are recorded in the gut but near minimal volumes, less then substrate ingested (Bertora et al., 2021).
So the picture of what Corydoradinae eat in the wild is unclear.
The Dietary Morphology of Corydoras
Figure 1: Hoplisoma trilineatum skeletal anatomy produced by computerized tomography (CT) scanning. Produced by: Lowe, A., Summers, A. P., Walter, R. P., Walker, S., & Paig-Tran, E. M. (2021). Scale performance and composition in a small Amazonian armored catfish, Corydoras trilineatus. Acta Biomaterialia, 121, 359-370.
Again, an unclear topic. We know Corydoradinae have oral jaws (Fig 1) at the front of the head humongous with our the general vertebrate jaw. These oral jaws contain teeth (Huysentruyt et al., 2011) but there seems to have been no exploration of the diversity of these teeth. These oral jaws are very similar to other invertivores (feeds on invertebrates), being elongate to extract food items out of crevices or the substrate.
What is not researched is the secondary pair of jaws found in most fishes, the pharyngeal jaws. While the oral jaws in fishes are often involved in prey capture, the pharyngeal jaws are involved in prey processing, so the grinding and breaking down. These are at the back of the mouth so aren’t obvious but when you see a fishes head move after feeding it’s likely those jaws are moving. Corydoradinae do have pharyngeal jaws, they contain teeth (Huysentruyt et al., 2011) but we have no idea how this morphology differs across Corydoradinae. In Osteogaster aenea Huysentruyt et al. (2011) identified elongate pharyngeal teeth which would confirm that at least O. aeneus is not evolved to feed on snails but the jaws do seem some what robust. It contrasts from those species that feed on algae to any extent who seem to have much more simplistic and often bladed pharyngeal anatomy. Most research into pharyngeal anatomy focuses on cichlids of which might not be the best reference given differential feeding behaviour.
Head shape can tell a lot about the fish, these fishes have such inferiorly facing mouths will be feeding around the substrate. What is more interesting is the shape of the snout mentioned earlier but we know so little about it. Those elongate snouts certainly allow the fish to dig deeper for food but how it effects them we only have clues.
What should I feed my Corydoras?
These are certainly not feeding on fishes, there is also the misconception that because fishes die that all fishes have access to them. Generally weaker individuals would be picked up by predators before they die and any dead fish would be more quickly exploited by species evolved to detect and quickly feed on carcasses. So fish meal is logically best avoided. These fishes also do not feed on plants so cereals are certainly of little use. This means those general diets are not great for them, most containing fish meal, cereals, vegetables etc. usually in that order.
Luckily for carnivores there is a few options for insect based foods. Fish Science is generally good and they offer some diversity. Fluval bug bites can be okay but still has quite a lot of fish meal and cereals in it. Repashy bottom scratcher is certainly worth looking at, being a gel diet you can add additional ingredients to it. I wouldn’t be afraid to use either Fish Science or Repashy bottom scratcher as the basis of the diet then frozen and freeze dried foods to build on it creating a more well rounded diet. Certainly live foods are worth looking at and would offer a lot of enrichment.
Corydoradinae are very forgiving regarding diets so experimenting is certainly possible.
Frozen foods are great but often will not contain all of the nutrition a species might require. In the wild most fishes will feed on hundreds of species and the narrow range of frozen foods available likely doesn’t compare nutritionally. These are great as enrichment or an addition to a fishes diet but not as a complete diet.
Protein Blisters
This is something that will always need mentioning regarding diets. I am not convinced it is caused by too much protein, even protein that isn’t absorbed/taken up by the fish e.g. excreted as nitrogenous waste. There is no evidence either way, it is clear bacteria can cause blisters and cysts but it can’t be said every cyst is caused by them without exploring further. Some frozen/live foods such as bloodworm can harbor Aeromonas (Senderovich et al., 2008) so it is difficult to make assumptions but there is little research on that.
A suggestion has been a form of gas bubble disease, true gas bubble disease as I call it though is caused from supersaturation of gases in the water, or some change in pressure resulting in bubbles forming in tissues very rapidly like the bends. It kills extremely rapidly as those bubbles form and burst blood vessels. There are other similar diseases like I have seen extreme algae growth associated, not proven though, to cause bubbles in some fishes but doesn’t kill and they are very localized.
We see similar in Loricariids, also armored and personally I would associate it with an infection of some kind. Blisters are tricky though as it’s such a general pathological symptom it could mean anything.
References:
Alexandrou, M. A., Oliveira, C., Maillard, M., McGill, R. A., Newton, J., Creer, S., & Taylor, M. I. (2011). Competition and phylogeny determine community structure in Müllerian co-mimics. Nature, 469(7328), 84-88.
Bertora, A., Fontanarrosa, M. S., Grosman, F., Sanzano, P., & Rosso, J. J. (2021). Trophic ecology of the Neotropical tolerant fish Corydoras paleatus under the influence of contrasting environmental conditions in a prairie stream. Anais da Academia Brasileira de Ciências, 93, e20200981.
Huysentruyt, F., Geerinckx, T., Brunain, M., & Adriaens, D. (2011). Development of the osteocranium in Corydoras aeneus (Gill, 1858) Callichthyidae, Siluriformes. Journal of Morphology, 272(5), 573-582.
Lowe, A., Summers, A. P., Walter, R. P., Walker, S., & Paig-Tran, E. M. (2021). Scale performance and composition in a small Amazonian armored catfish, Corydoras trilineatus. Acta Biomaterialia, 121, 359-370.
Nijssen, H. (1970). Revision of the Surinam catfishes of the genus Corydoras Lacépède, 1803 (Pisces, Siluriformes, Callichthyidae). Beaufortia, 18(230), 1-75.
Senderovich, Y., Gershtein, Y., Halewa, E., & Halpern, M. (2008). Vibrio cholerae and Aeromonas: do they share a mutual host?. The ISME journal, 2(3), 276-283.
Žák, J., Roy, K., Dyková, I., Mráz, J., & Reichard, M. (2022). Starter feed for carnivorous species as a practical replacement of bloodworms for a vertebrate model organism in ageing, the turquoise killifish Nothobranchius furzeri. Journal of Fish Biology, 100(4), 894-908.
This is one of the most controversial topics and why not? It involves some really detailed physiology and multiple processes. Generally this means getting your head around things you cannot usually see. I shall only discuss juvenile and adult fishes rather then their eggs here.
First is to understand the anatomy we are discussing in relation to the topic, this is largely the gills found in all fishes.
Figure 1: A diagram of the gills by Campbell, N. A., Reece, J. B., Taylor, M. R., Simon, E. J., & Dickey, J. (2006). Biology: concepts & connections (pp. 70-78). San Francisco, CA: Benjamin Cummings.
The gills while largely known for taking up O2 and release CO2 so have a role in respiration this organ has other purposes. Two major functions are maintenance in osmoregulation and processing of nitrogenous waste, ammonium (NH4+). You can see that the gills are split into gill arches which support two gill filaments, these filaments are then made of many small structures called lamellae (Fig 1). The aim of these structures is to increase surface area so exposure to the water for these purposes.
Another organ that might be discussed is the kidneys, but forget whatever you previously thought about kidneys, fishes kidneys look very different. The structure isn’t really of much use to us but it is generally a thin stretched structure at the top of the fish if curious this website is great for necropsy images: https://www.necropsymanual.net/en/teleosts-anatomy/excretory-and-osmo-regulatory-system/
So lets get into the real physiology.
pH
pH to put simply is a measure of hydrogen ions (H+, reduces the pH) and hydroxide (OH–, increases the pH), it measured in a logarithmic scale so a pH of 6 is 10x more acidic then a pH of 7.
This measure has two main interactions with fishes ammonia excretion and uptake/maintenance of minerals within fishes.
High pH
Ammonia generally exists in two states ammonia (NH3) and ammonium (NH4+). At higher pH levels ammonia is the dominant compound, at lower pH’s it is converted to the safer ammonium. At a higher pH environment the fish has a reduced ability to transport ammonia out of the body, leading to accumulation within the fishes body (Eddy & Handy, 2012; Wilkie & Wood, 1996).
Low pH
It is well known fishes take up calcium (Ca2+) and sodium (Na+) from their environment, it is important for many biological processes. H+, in higher volumes in low pH water competes with calcium and sodium to be taken up by the fishes. In a similar process to how a high pH results in high ammonia accumulation a low pH increases excretion of ammonium (Malabarba et al., 2020). Although a low pH is not particularly toxic (Eddy & Handy, 2012), it does limit access to these compounds. Many fishes who inhabit these environments have evolved different physiological responses to allow them to inhabit such an environment.
One interaction of a low pH would be that this erodes rocks even slowly that can allow for aluminum to accumulate in it’s more toxic form, Al3+(Eddy & Handy, 2012). This shouldn’t be an issue in a well water changed aquarium, but could be a contributor to “old tank syndrome”.
Regardless this is generally discussed at extremes and not usually the parameters we keep our fishes in.
Hardness, the various measures under that name
Hardness maybe is more complex, the aquarium trade associates it largely with KH or GH but realistically there are so many compounds involved that we are not testing for. These compounds are what is discussed in the scientific literature (Malabarba et al., 2020). I prefer TDS or conductivity, not just are these likely the only measures you’ll find for wild fishes.
Low hardness
At a low hardness ionic balance as discussed in the pH section would become difficult. This results in the increase in cells that maintain this balance known as ionocytes (Malabarba et al., 2020).
High hardness
High hardness can result in stress from calcium in the gills, liver and intestines at extreme levels but fishes do show the ability to adapt (Limbaugh et al., 2012).
Adaptability
Many fishes clearly display adaptations to deal with extremes, this depends on the species to it’s ideal range and what it can deal with (Eddy & Handy, 2012; Malabarba et al., 2020). So unless a species has been studied we really don’t know how much they can adapt to.
Summary
It is really difficult to say how compounds interact with fishes in the aquarium context, we are dealing with such a comparatively narrow range of parameters. Recently people have been even avoiding the extremes on the lower side so it’s become difficult to say to much. This topic unlike many is discussing such a wide diversity of taxa and many inhabit variable regions.
References:
Campbell, N. A., Reece, J. B., Taylor, M. R., Simon, E. J., & Dickey, J. (2006). Biology: concepts & connections (pp. 70-78). San Francisco, CA: Benjamin Cummings.
Eddy, B., & Handy, R. D. (2012). Ecological and environmental physiology of fishes (Vol. 4). Oxford University Press.
Limbaugh, N., Romano, N., Egnew, N., Shrivastava, J., Bishop, W. M., & Sinha, A. K. (2021). Coping strategies in response to different levels of elevated water hardness in channel catfish (Ictalurus punctatus): Insight into ion-regulatory and histopathological modulations. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 260, 111040.
Malabarba, L. R., Malabarba, M. C., Baldisserotto, B., Urbinati, E., & Cyrino, J. (2020). Biology and physiology of freshwater neotropical fish. Academic Press.
Wilkie, M. P., & Wood, C. M. (1996). The adaptations of fish to extremely alkaline environments. Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 113(4), 665-673.
Choosing fish foods can be very confusing, there are many products on the market all with various claims. The majority of fish diets are formulated based on the nutrition for food fishes, these diets have an aim to have a high growth rate while minimizing costs, efficiency would be the best term. The aim of the ornamental aquarist is far from that, we want a long lived healthy fish with good coloration. The nutritional composition requirements are differ between the two aims (Vucko et al., 2017). This has resulted in many diets not catering for the aim of the fishkeeper and no where is this more obvious then diets aimed at plecos, Loricariids.
The majority of Loricariids are algivores or detritivores, but there is a diversity of dietary niches (Lujan et al., 2015). Contrastingly many products labelled as pleco or algae wafers/pellets contain little to no algae but higher proportions of fish meal (Vucko et al., 2017). The majority of popular Loricariids are along the lines of algivory or feed on various volumes so this should be a focus for the aquarist. Additionally I have yet to see fish ever recorded in the gut of any Loricariid.
These fishes are the most difficult to cater for giving there isn’t quite the selection of algaes available in any diet. Some of them can be difficult for the fish to take to so hence I find Repashy soilent green good and can then be bulked out with even more algae’s.
Catering for Carnivores.
I am not really discussing carnivores so much in this article as there are many diets that cater for them and in recent years with the focus into invertebrates it is only improving. Still, many diets are very high in fish meals, something Loricariids do not consume and nutritionally these do not compare. Not just can fish meals be different nutritionally, the nutrients can be difficult to access (Žák et al., 2022).
The great thing for carnivores is the diversity of frozen foods we have available within the hobby and even fishmongers. Although keep aware for the enzyme thiaminase (in mussels and some fishes) and limit the frequency these are fed to your fishes.
Other niches and specialization.
Fungi hyphae are found in the diets of Panaque, Panaqolus and the Hypostomus cochliodon group and are likely digested, mushrooms or mycoproteins would be the closest to replicating this (Lujan et al., 2011). Sadly most diets don’t contain these. It would be interesting to feed wood that has many of these but usually by the point they have obvious hyphae they are almost entirely broken down.
While Hypancistrus are largely algivores, there is evidence a few of them feed on seeds, read about Hypancistrus here. The exception being Hypancistrus vandragti who seems a little more carnivorous in comparison (Lujan & Armbruster, 2011).
Will they eat it?
Something few consider is that just because a diet might be amazing with ingredients they might not eat it. So there are a range of ingredients such as some herbs used entirely to encourage fishes to eat a diet. This has been the issue I’ve found with some that have great ingredients Repashy super green for example.
Premade diets and their ingredients
Premade diets unlike if you were to make anything yourself entirely will have a reasonable range of nutrients. They are best more as a basis to work from for a more well rounded diet.
From these tables it is easy to understand the varying suitability of different diets to different species and genera. The colour coding is only to give an idea as many ingredients have multiple purposes e.g. fish meal can be a binding agent as well as for nutrition.
Ingredients are ordered in quantity so the top of the list contributes the most.
The hidden issue with premade diets
There is a hidden issue, as you look across the table how similar are many of these diets? Many fishkeepers will buy a range of different products in the aim of diversity of nutrition and ingredients. If so many of the ingredients and the orders are similar this means that there is little diversity, the exception would be there the major ingredients are very different.
Products sold for plecos
Company
Repashy
Product
Soilent Green
Super Green
Bottom scratcher
Morning wood
Dietary Niche
Algivory
Algivory
Carnivory
Xylovory
Summary
Fishes tend to prefer this diet. Contains mostly algae but has a some animal meals but can be bulked out with more algae’s.
Contains no animal products. Fish seem less keen on it. High in algae’s.
Contains a diversity of invertebrates. Shouldn’t be fed as the only diet for non-carnivores as can lead to bloat e.g. Hypancistrus.
No Loricariids digest wood, cellulose is the main ingredient.
Repashy products, coloured by type of product; algae (Dark green), Plant Matter (blue), cereal (Orange), animal matter (red), vitamins (pink), not highlighted might have other purposes such as binding agents or other nutrition.
Repashy unlike the other brands is a gel diet, this means other products such as algae powders can be added in. This means for any of them you can increase the algal composition or add ingredients such as basil.
Company
Fluval
AquaCare
Product
Bug Bites Pleco Sticks
Bug Bites Pleco Crisps
Spirulina Sinking Wafers
Oak
Dietary Niche
Carnivore
Omnivore/cereals
Omnivore
Omnivore/cereals
Summary
A reasonable amount of insects so more ideal then those with more fish meals for carnivores.
A smaller amount of insect meals and contains a wider range of cereals.
Mostly fish meal with a lot of cereals, little algae.
Loricariids cannot digest wood/cellulose nor is it used for digestion. Mostly wheat, which will have limited nutrition and a high amount of fish meal.
Coloured by type of product; algae (Dark green), Plant Matter (blue), cereal (Orange), animal matter (red), vitamins and minerals (pink), not highlighted might have other purposes such as binding agents or other nutrition.
Company
Hikari
Dr Bassler
Vitalis
Product
Algae Wafers
Green
Regular
Pleco Pellets
Dietary Niche
Omnivore
Omnivore
Omnivore
Omnivore
Summary
Not ideal. Contains a lot of fish meal and cereals. A general diet that targets no species.
Very high in cereals and fish meals. Too few algaes to cater for an algivore.
Pretty much the same as the green diet. A lot of fish meal and cereals.
Not ideal. A very general diet that doesn’t cater for any species. Mostly contains fish.
Cereals, fish and fish derivatives, derivatives of vegetable origin, Chlorella pyrenoidosa (5 %), Moringa oleifera (5 %), molluscs and crustaceans, yeast, minerals Additives: Vitamins: E672 Vitamin A 7,500 IE/kg, E671 Vitamin D3 2,500 IE/kg , E300 Vitamin C 500 mg/kg, E307 Vitamin E 260 mg/kg, Magnesium 400 mg/kg, Iron 300 mg/kg, Omega-3 fatty acids 50 mg/g, Vitamin B3 7.5 mg/kg, Chlorophyll 2 mg/kg, Folic acid 2 mg/kg, Selenium 1 mg/kg, Iodine 0.02 mg/kg
Fish and fish derivatives, cereals, molluscs and crustaceans, derivatives of vegetable origin, yeast, minerals Additives: Vitamins: E672 vitamin A 7500 IU/kg, E671 vitamin D3 2500 IU/kg, E300 vitamin C 500 mg/kg, E307 vitamin E 260 mg/kg
Fish and Fish Derivatives, Derivatives of Vegetable Origin, Algae, Oils and Fats, Minerals, Molluscs and Crustaceans.
Coloured by type of product; algae (Dark green), Plant Matter (blue), cereal (Orange), animal matter (red), vitamins (pink), not highlighted might have other purposes such as binding agents or other nutrition.
Company
Oase
Tetra
New Life Spectrum
Fish Science
Product
Organix Veggievore Tabs
Spirulina Wafers
Algae Max
Algae wafers
Dietary Niche
Carnivore
Herbivore
Algivore
Omnivore
Summary
A lot of fish/shrimp meals. Only a small amount of krill.
Plant focused but lacks a lot of algaes.
Beware some have higher fish meal volumes. Otherwise a great range of algaes.
Would benefit from more algaes, the use of mycoproteins is interesting but still a large amount of cereals and fish meal.
Algae (Spirulina & Kelp 15%), Mycoprotein, Cereals, Herring meal, Vegetable protein extracts, Insect meal, Vegetables (Cucumber, Spinach), Molluscs and crustaceans, Yeast, Salmon oil and Garlic.
Coloured by type of product; algae (Dark green), Plant Matter (blue), cereal (Orange), animal matter (red), vitamins (pink), not highlighted might have other purposes such as binding agents or other nutrition.
References:
Lujan, N. K., & Armbruster, J. W. (2011). Two new genera and species of Ancistrini (Siluriformes: Loricariidae) from the western Guiana Shield. Copeia, 2011(2), 216-225.
Lujan, N. K., German, D. P., & Winemiller, K. O. (2011). Do wood‐grazing fishes partition their niche?: morphological and isotopic evidence for trophic segregation in Neotropical Loricariidae. Functional Ecology, 25(6), 1327-1338.
Lujan, N. K., Winemiller, K. O., & Armbruster, J. W. (2012). Trophic diversity in the evolution and community assembly of loricariid catfishes. BMC Evolutionary Biology, 12, 1-13.
Vucko, M. J., Cole, A. J., Moorhead, J. A., Pit, J., & de Nys, R. (2017). The freshwater macroalga Oedogonium intermedium can meet the nutritional requirements of the herbivorous fish Ancistrus cirrhosus. Algal research, 27, 21-31.
Žák, J., Roy, K., Dyková, I., Mráz, J., & Reichard, M. (2022). Starter feed for carnivorous species as a practical replacement of bloodworms for a vertebrate model organism in ageing, the turquoise killifish Nothobranchius furzeri. Journal of Fish Biology, 100(4), 894-908.
Company
Product
Dietary Niche
Summary
Composition (%):
Protein
Fat
Fibre
Moisture
Ash
Ingredients
Coloured by type of product; algae (Dark green), Plant Matter (blue), cereal (Orange), animal matter (red), vitamins (pink), not highlighted might have other purposes such as binding agents or other nutrition.
There are few fishes that really catch the eye as much as the order of true knifefishes, Gymnotiformes. Sometimes confused with some Asian and African species from the group Notopteridae which is within the family Osteoglossiformes, also within that group is the arowana. Gymnotiformes are restricted to South America with the closest relatives being Siluriforme (catfishes) and the tetras (Characiformes) both groups who have a much wider distribution.
Figure 1: Phylogeny of Loricariidae according to molecular information (Tagliacollo et al., 2016): Tagliacollo, V. A., Bernt, M. J., Craig, J. M., Oliveira, C., & Albert, J. S. (2016). Model-based total evidence phylogeny of Neotropical electric knifefishes (Teleostei, Gymnotiformes). Molecular phylogenetics and evolution, 95, 20-33.
Gymnotiforme contains 6 families, 36 genera and 272 species (Fricke et al., 2024). Of these species only one is a frequent import, Apternotus albifrons with the common name black ghost knifefish. Other species do appear in the trade but much less frequently otherwise this article would be more specific.
Morphology
The order is generally identified by an eel (anguilliform) shaped body, a large anal fin that extends across the majority of the fishes abdomen, no dorsal/adipose/pelvic fins and; a caudal fin might be present but reduced (Tagliacollo et al., 2016).
The largest Gymnotiformes are in the genus Electrophorus, electric eels of which comprises 4 species, with evidence of individuals reaching over 120cm TL (de Santana et al., 2019). While the smallest might be Hypopygus minissimus at 6.4cm SL (de Santana & Crampton, 2011).
The largest amount of diversity of this family would be in the head shape, there are many with shorter heads and extremely gape limited, others with elongated jaws, some with wide jaws and quite a few with a long snout like mouth. This likely reflects their diet, while all are carnivores there is a wide range of different prey various genera will specialize in (Albert & Crampton, 2005; Ford et al., 2022).
Gymnotus javari
Colouration is extremely variable although they lack any vivid colours the markings differ based likely on the environment. My personal favorite’s for colouration are the various striped members of the genus Gymnotus.
The complexity of dietary specialization
As mentioned earlier Gymnotiformes display a wide diversity of jaw and mouth shapes, some are likely more generalists and others much more specialized. A large number of genus that occur on the rare occasion tend to be these specialists.
Gymnotiformes are all carnivores and many invertivores/insectivores (Gonçalves-Silva et al., 2022; Giora et al., 2014). Some feed on particularly small food items for their relative body size. Lundberg & Mago-Leccia (1986) displayed many species feeding exclusively on plankton regardless of their body size of 8-14cm SL in some of these species. This planktivorous diet is found in many of these long nosed and gape limited species (Giora et al., 2014; Lundberg & Mago-Leccia, 1986). These species simply cannot feed on larger food items and seems to display preferences additionally on the food item. I can only recommend for these trying many different frozen and live foods in a tank with nothing that can compete but even if feeding they can be a challenge and I do not recommend. Feeding these species takes time and requires space for culturing live food, they are probably best species only.
There are genera that do work within captivity although very few. Apternotus albifrons and A. leptorhynchus the brown and black ghost knifefish, not to be confused with a Notopteridae the brown knifefish, Xenomystus nigri from Africa. These have larger mouths that extend so can even feed on tetra but due to their adult size of 30cm SL (Mucha et al., 2021) but in the aquarium some suggest 50cm. This makes them a bit of an undertaking, so the social X. nigri might be a better choice at about 11-15cm SL (Golubtsov & Darkov, 2008). X. nigri has a more extreme arched back, solid grey/black/brown colouring and the anal fin connects directly to the caudal fin. Gymnotus is the other appropriate genus to the aquarium, it is variable in size from around 15cm for Gymnotus javari to 60cm for Gymnotus carapo (Craig et al., 2019). The mouth of Gymnotus doesn’t open as wide as Apternotus and is generally a more shy fish, so would need much less competition. Gymnotus does provide a problem as while there is such a range in size the species provide issues for the fishkeeper in identifying, often small differences. G. carapo vs G. javari is at least easier, the former has the most vivid colouring with distinct black and white wide stripes maybe with spots but I think is slightly more arched in the back.
Sternarchorhynchus aff. mormyrus at night.
Feeding these two genera then if they can be fed on fry foods is the best for the range of vitamins, minerals and general nutrition. Otherwise Gymnotus can be a little more specialized requiring freeze dried, frozen or live foods but are at least generalists. For Gymnotus a range of frozen and freeze dried foods is a must but on top look around for different live foods appropriate for their mouth size, I feed my G. javari earthworms in terms of live foods to avoid those I cannot culture.
This is not typically a genus for the majority of tanks but they are illusive fishes regardless so take the real pet rock fish enthusiast. Gymnotus and two of the Apternotus would be the best choice for the majority of people.
Black ghost knifefish, Apternotus albifrons from Derek Ramsey (2005).
Habitat and setup
Gymnotiforme’s are illusive fishes, they will spend most of their time hiding whether it be in caves or some species will bury themselves in the sand (Escamilla-Pinilla et al., 2019). Therefore a wide diversity of different hiding spaces are a must for these fishes, while some might suggest glass caves given these fishes have eyes they can detect light and dark and would feel safer in a dark area.
There is quite the diversity in habitats but the majority of specialists are maybe more riparian/marginal species. Many of these smaller specialists species would enjoy a habitat with many botanicals or plants (Crampton, 2016) but this might not be possible due to trapping food although if lucky it could encourage smaller invertebrates like ostracods. While others exploit deep channels of water (Evans et al., 2019) therefore without these botanicals or leaf litter but large wood/and or rocks would be present. These found in areas of high botanicals it would be worth considering that they inhabit areas of very low pH and conductivity (Bichuette & Trajano, 2015). Of the larger more adaptable species inhabit a wider range of habitats, Gymnotus is shown to prefer a rocky habitat although can be found at surprisingly high pH (7.6-7.8) and conductivities of (170-190 uScm-1) according to Richer-de-Forges et al. (2009) .
Sociality
As with many fishes there are social Gymnotiformes and those less so. Many are social although as a curiosity Apternotus females are shown to be social whereas the males are ill-tolerant of other individuals (Henninger et al., 2020; Dunlap & Larkins‐Ford, 2003). Similarly Gymnotus javari are suggested to be social whereas the majority of the genus doesn’t tolerate other individuals (Westby & Box 1970; https://www.youtube.com/watch?v=OMRu_YUBE34). The more specialist species seem to be so much more social and even then many fishes seem to learn to feed from each other.
Identification
Outside of the two groups I recommend most the issue has to be identification and I have given clues how to identify a few. There is a lot more diversity and this makes this group tricky. It is certainly a taxa delving into the scientific literature outside of Apternotus where the black and brown ghost knives are obvious. So this does mean Gymnotus is a little risky with obtaining a species that can grow much larger.
Conclusion
To write a whole article about Gymnotiformes without mentioning their amazing electrical abilities, well that doesn’t entirely concern us as fishkeepers with the exception of Electrophorus, the electric eel of which needs an article of it’s own. These are also likely very intelligent fishes who would benefit from a tank that has a variety of decor and landscapes.
References:
Albert, J. S., & Crampton, W. G. (2005). Diversity and phylogeny of Neotropical electric fishes (Gymnotiformes). In Electroreception (pp. 360-409). New York, NY: Springer New York.
Bichuette, M. E., & Trajano, E. (2015). Population density and habitat of an endangered cave fish Eigenmannia vicentespelaea Triques, 1996 (Ostariophysi: Gymnotiformes) from a karst area in central Brazil. Neotropical Ichthyology, 13, 113-122.
Craig, J. M., Kim, L. Y., Tagliacollo, V. A., & Albert, J. S. (2019). Phylogenetic revision of Gymnotidae (Teleostei: Gymnotiformes), with descriptions of six subgenera. PLoS One, 14(11), e0224599.
Crampton, W. G., De Santana, C. D., Waddell, J. C., & Lovejoy, N. R. (2016). Phylogenetic systematics, biogeography, and ecology of the electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes). PLoS One, 11(10), e0161680.
de Santana, C. D., & Crampton, W. G. (2011). Phylogenetic interrelationships, taxonomy, and reductive evolution in the Neotropical electric fish genus Hypopygus (Teleostei, Ostariophysi, Gymnotiformes). Zoological Journal of the Linnean Society, 163(4), 1096-1156.
de Santana, C. D., Crampton, W. G., Dillman, C. B., Frederico, R. G., Sabaj, M. H., Covain, R., … & Wosiacki, W. B. (2019). Unexpected species diversity in electric eels with a description of the strongest living bioelectricity generator. Nature communications, 10(1), 1-10.
Dunlap, K. D., & Larkins‐Ford, J. (2003). Production of aggressive electrocommunication signals to progressively realistic social stimuli in male Apteronotus leptorhynchus. Ethology, 109(3), 243-258.
Escamilla-Pinilla, C., Mojica, J. I., & Molina, J. (2019). Spatial and temporal distribution of Gymnorhamphichthys rondoni (Gymnotiformes: Rhamphichthyidae) in a long-term study of an Amazonian terra firme stream, Leticia-Colombia. Neotropical Ichthyology, 17, e190006.
Evans, K. M., Kim, L. Y., Schubert, B. A., & Albert, J. S. (2019). Ecomorphology of neotropical electric fishes: an integrative approach to testing the relationships between form, function, and trophic ecology. Integrative Organismal Biology, 1(1), obz015.
Ford, K. L., Bernt, M. J., Summers, A. P., & Albert, J. S. (2022). Mosaic evolution of craniofacial morphologies in ghost electric fishes (Gymnotiformes: Apteronotidae). Ichthyology & Herpetology, 110(2), 315-326.
Giora, J., Tarasconi, H. M., & Fialho, C. B. (2014). Reproduction and feeding of the electric fish Brachyhypopomus gauderio (Gymnotiformes: Hypopomidae) and the discussion of a life history pattern for gymnotiforms from high latitudes. PloS one, 9(9), e106515.
Golubtsov, A. S., & Darkov, A. A. (2008). A review of fish diversity in the main drainage systems of Ethiopia based on the data obtained by 2008. In Ecological and faunistic studies in Ethiopia, Proceedings of jubilee meeting “Joint Ethio-Russian Biological Expedition (Vol. 20, pp. 69-102). Moscow: KMK Scientific Press.
Gonçalves-Silva, M., Luduvice, J. S., Gomes, M. V. T., Rosa, D. C., & Brito, M. F. (2022). Influence of ontogenetic stages and seasonality on the diet of the longtail knifefish Sternopygus macrurus (Gymnotiformes, Sternopygidae) in a large Neotropical river. Studies on Neotropical Fauna and Environment, 57(1), 11-17.
Henninger, J., Krahe, R., Sinz, F., & Benda, J. (2020). Tracking activity patterns of a multispecies community of gymnotiform weakly electric fish in their neotropical habitat without tagging. Journal of Experimental Biology, 223(3), jeb206342.
Lundberg, J. G., & Mago-Leccia, F. (1986). A review of Rhabdolichops (Gymnotiformes, Sternopygidae), a genus of South American freshwater fishes, with descriptions of four new species. Proceedings of the Academy of Natural Sciences of Philadelphia, 53-85.
Mucha, S., Chapman, L. J., & Krahe, R. (2021). The weakly electric fish, Apteronotus albifrons, actively avoids experimentally induced hypoxia. Journal of Comparative Physiology A, 207(3), 369-379.
Richer-de-Forges, M. M., Crampton, W. G., & Albert, J. S. (2009). A new species of Gymnotus (Gymnotiformes, Gymnotidae) from Uruguay: description of a model species in neurophysiological research. Copeia, 2009(3), 538-544.
Tagliacollo, V. A., Bernt, M. J., Craig, J. M., Oliveira, C., & Albert, J. S. (2016). Model-based total evidence phylogeny of Neotropical electric knifefishes (Teleostei, Gymnotiformes). Molecular phylogenetics and evolution, 95, 20-33.
Westby, G. M., & Box, H. O. (1970). Prediction of dominance in social groups of the electric fish, Gymnotus carapo. Psychonomic Science, 21(3), 181-183.
Many fishes display lumps, spots and bumps which can happen due to a range of pathological conditions whether it being pathogens or other factors. These can easily be confused and if concerned or confused please consult a fish pathologist or trained fish specialist veterinarian. This page is only to help give some clarity
All sources here are from scientific papers and many of the images from these papers for a reliable diagnosis unless otherwise stated for clarity purposes.
Microscopy is required in many cases for a confirmed diagnosis and therefore I recommend their use. Some stores might have one available to be used. In other cases more advanced diagnostic techniques might be required and provided by a pathologist via a veterinarian.
Protozoan ciliate pathogen which can cause large mortalities in later stages.
Ichthyophthirius multifiliis on a Rift Valley cichlid, Aulonocara sp.? Image obtained from: Thomas Kaczmarczyk (www.djpalme.de.vu) on Wikipedia.
Occurrence: Seems to be very common and in my opinion largely occurs when fish are sufficiently stressed.
Diagnostics: White spots on the body of the fish, can also be accompanied by shedding of the slime coat. The spots can be varied in size and number. This ciliate additionally targets the gills where it causes the most stress on the fish (Yang et al., 2023; Mallik et al., 2013). This spotted appearance is commonly confused with Epistylis which if symptomatic (of which mostly it is not) appears more as a plaque so will not appear in this article (ESHA video; Ksepka et al., 2021; Valladao et al., 2015; Wang et al., 2017, Wu et al., 2021). Both pathogens can appear with Aeoromonas bacteria that additionally causes hemorrhaging (Kumar et al., 2022).
Microscopic image:
Ichthyophthirius multifiliis under the microscope, images obtained from Yang et al (2023). Yang, H., Tu, X., Xiao, J., Hu, J., & Gu, Z. (2023). Investigations on white spot disease reveal high genetic diversity of the fish parasite, Ichthyophthirius multifiliis (Fouquet, 1876) in China. Aquaculture, 562, 738804.
Treatment: The most frequent treatments provided in the aquarium hobby is malachite green with either formalin, formaldehyde or copper. Obviously copper is often a concern for those with invertebrates in the aquarium. Salt the old age treatment can work and as a study ABDULLAH-AL MAMUN et al. (2021) infers it depends on time of treatment. There seems to be a multitude of papers narrowing down the best treatment and to me this infers maybe there is no real answer, there might be increasing immunity of the ciliate or just this species is so diverse. Generally it’s assumed the best method is to avoid introducing any fish showing symptoms or on the same system with those who do. Copper sulphate additionally has been shown to treat white spot (Schlenk et al., 1998). In a later 2008 study formalin did not have any effect on the ciliate whereas copper treated it within 14 days (Rowland et al., 2008) which is around two rounds of treatment by most bottles. I therefore just looking at these three studies would not recommend formalin and maybe therefor formaldehyde for treatment and instead focus on copper and maybe salt needs further examination.
Velvet (Oodinium, Piscinoodinium and other dinospores) and related taxa
One of the most unusual parasites of fishes being an algae known as dinoflagellates.
Piscinoodinium pillulare outbreaks: piscinootest. Ciência Rural, 48. on the gills of a fish (Gomes et al., 2018). Gomes, A. L. S., Costa, J. I. D., Benetton, M. L. F. D. N., Bernardino, G., & Belem-Costa, A. (2018). A fast and practical method for initial diagnosis of Piscinoodinium pillulare outbreaks: piscinootest. Ciência Rural, 48.Piscinoodinium spp. infections (Esmail et al., 2015). Image obtained from: Esmail, M. Y., Astrofsky, K. M., Lawrence, C., & Serluca, F. C. (2015). The biology and management of the zebrafish. In Laboratory animal medicine (pp. 1015-1062). Academic Press.
Occurrence: Reasonably common, I can’t comment on cause. It seems Oodinium seems to be less common then Piscinoodinium.
Diagnostics: Different from white spot, being algaes they tend to have some coloration to them. Usually appears as small golden spots across the body, the fish are often lethargic. Mortality is not particularly rapid (Levy et al., 2007). It is not always obvious beyond hemorrhaging (Sudhagar et al., 2022).
Microscopic image: Not entirely required and diverse, although can make it easier to compare.
Piscinoodinium sp. copied from Sudhagar et al. (2022). Sudhagar, A., Sundar Raj, N., Mohandas, S. P., Serin, S., Sibi, K. K., Sanil, N. K., & Raja Swaminathan, T. (2022). Outbreak of Parasitic Dinoflagellate Piscinoodinium sp. Infection in an Endangered Fish from India: Arulius Barb (Dawkinsia arulius). Pathogens, 11(11), 1350.
Treatment: Treatment rarely seems discussed. As these are photosynthetic I agree with many aquarists that keeping the lights off for even two weeks will not harm the fish and even if it minorly effects the algae that’s better then nothing. The aquarium hobby largely jumps to copper based treatments along with malachite green mixed in with methylene blue, it doesn’t seem the most resistant pathogen and I wonder additionally if a fishes immune system handles some of it. Copper is suggested to work (Lieke et al., 2020). There seems to be no research on methylene blue other then being an anti-protozoan compound. Similarly with malachite green, no treatments even salt have any strong background to their effectiveness. The other issue is these compounds can effect the microbes within the aquarium (Yang et al., 2021). All I can say is I had success with the NT labs anti-parasite treatment containing copper sulphate and formaldehyde along with switching the lights off.
Dermocystidium
The strangest in appearance of pathogens, much like a worm but far from that, their taxonomic placement is unclear but they don’t move.
Dermocystidium on a hatchet fish, Gasteropelecus.
Occurrence: Reasonably frequent with a diversity of fishes soon after obtaining.
Diagnostics: Worm like in a variety of forms and size, can be encapsulated by pectoral fins or around the body. Some might appear singularly other fishes might have a lot more. These do not move like nematodes but are extremely diverse (Fujimoto, et al., 2018; Persson et al., 2022).
Microscope image: Not required.
Treatment: It is largely agreed in the aquarium trade which I agree that these protozoans as unsightly as they are do disappear with time and handled by the fishes own immune system.
Worm cysts
Not really possible to obtain much scientific research on the topic with the time I have free. But it does happen and seems frequent with wild imports.
Occurrence: Not common at all, seems to arrive with import.
Diagnostics: Looks much like white spot but larger cysts. Stubborn and white spot treatments do not work regardless of the fish showing no lethargy or poor health.
Microscope image: Usually distinctively different from white spot velvet by size and shape.
Treatment: As suggested by the name, wormers tend to work. I cannot remember which I used but likely first praziquantel, levamisole and flubendazole might work as well.
Tumors
If a tumor occurs certainly this is a situation where veterinarians are recommended.
Occurrences: There are many caused within fishes, sometimes it is genetic causes such as in the dragon scale of Betta splendens, viral causes (Coffee et al., 2013) or dietary (Žák et al., 2022). On a quick scan of the literature papilloma viruses are not associated with tumors.
Diagnosis: These can be large growths, they can be vascularized supplied by blood vessels. Unlike viral growths on my observations tend to be rounder and do not appear in many numbers.
Microscopy: Not required.
Treatment: Discuss with a specialist fish veterinarian.
Viral papilloma and herpes viruses
These are commonly mistaken for lymphocystis and can be very complex growths. Technically Papilloma refers to epithelial groups but can display similarly to herpes viruses. In the aquarium trade it doesn’t seem clear which we are handling and regardless treatment is the same. A wide range of herpes viruses are associated with fishes from KHV, carp pox (Davison et al., 2013) and channel catfish herpesvirus (Davison et al., 1992).
Viral papilloma’s likely caused by a Papillomavirus (PV) in a Pterygoplichthys pardalis, image sourced from Reddit, poster: Render et al., 1721.
Occurrence: Seems reasonably common right now. This virus I can assume once contracted is not removed from the fishes body but are suppressed by the immune system. Koi Herpes Virus (KHV) is fatal and while not wildly common any suspected occurrence might require contacting environmental authorities.
Diagnosis: These are round or very tuberous numerous growths, much more like warts while symptomatic but asymptomatic individuals and time might not display any symptoms (Tarján et al., 2022; Rahmati-Holasoo et al., 2015). Very understudied when it comes to aquarium fishes so whether we are dealing with a herpes or traditional papilloma virus is difficult to say. Rahmati-Holasoo et al. (2015) infers that most viral growths we are seeing in Loricariids is caused by a Papillomavirus, although a previous study by Hedrick et al., (1996) in carp inferred similar growths and concluded due to a herpes virus.
Treatment: Time, these viruses cannot be cured only prevention of introduction. Very few are fatal. These viruses are generally specific to closely related fishes so transfer should not be an issue.
There is a wide range of unknown growths in fishes we can only make assumptions, veterinary professionals and vets would be worth consulting. I have seen a number which didn’t conform with any of these.
References:
ABDULLAH-AL MAMUN, M. D., NASREN, S., RATHORE, S. S., & RAHMAN, M. M. (2021). Mass infection of Ichthyophthirius multifiliis in two ornamental fish and their control measures. Annals of Biology, (2), 209-214.
Coffee, L. L., Casey, J. W., & Bowser, P. R. (2013). Pathology of tumors in fish associated with retroviruses: a review. Veterinary Pathology, 50(3), 390-403.
Davison, A. J. (1992). Channel catfish virus: a new type of herpesvirus. Virology, 186(1), 9-14.
Davison, A. J., Kurobe, T., Gatherer, D., Cunningham, C., Korf, I., Fukuda, H., … & Waltzek, T. B. (2013). Comparative genomics of carp herpesviruses. Journal of Virology, 87(5), 2908-2922.
Esmail, M. Y., Astrofsky, K. M., Lawrence, C., & Serluca, F. C. (2015). The biology and management of the zebrafish. In Laboratory animal medicine (pp. 1015-1062). Academic Press.
Fujimoto, R. Y., Couto, M. V. S., Sousa, N. C., Diniz, D. G., Diniz, J. A. P., Madi, R. R., … & Eiras, J. C. (2018). Dermocystidium sp. infection in farmed hybrid fish Colossoma macropomum× Piaractus brachypomus in Brazil. Journal of Fish Diseases, 41(3), 565-568.
Gomes, A. L. S., Costa, J. I. D., Benetton, M. L. F. D. N., Bernardino, G., & Belem-Costa, A. (2018). A fast and practical method for initial diagnosis of Piscinoodinium pillulare outbreaks: piscinootest. Ciência Rural, 48.
Hedrick, R. P., Groff, J. M., Okihiro, M. S., & McDowell, T. S. (1990). Herpesviruses detected in papillomatous skin growths of koi carp (Cyprinus carpio). Journal of Wildlife Diseases, 26(4), 578-581.
Ksepka, S. P., & Bullard, S. A. (2021). Morphology, phylogenetics and pathology of “red sore disease”(coinfection by Epistylis cf. wuhanensis and Aeromonas hydrophila) on sportfishes from reservoirs in the South‐Eastern United States. Journal of Fish Diseases, 44(5), 541-551.
Kumar, V., Das, B. K., Swain, H. S., Chowdhury, H., Roy, S., Bera, A. K., … & Behera, B. K. (2022). Outbreak of Ichthyophthirius multifiliis associated with Aeromonas hydrophila in Pangasianodon hypophthalmus: The role of turmeric oil in enhancing immunity and inducing resistance against co-infection. Frontiers in immunology, 13, 956478.
Levy, M. G., Litaker, R. W., Goldstein, R. J., Dykstra, M. J., Vandersea, M. W., & Noga, E. J. (2007). Piscinoodinium, a fish-ectoparasitic dinoflagellate, is a member of the class Dinophyceae, subclass Gymnodiniphycidae: convergent evolution with Amyloodinium. Journal of Parasitology, 93(5), 1006-1015.
Lieke, T., Meinelt, T., Hoseinifar, S. H., Pan, B., Straus, D. L., & Steinberg, C. E. (2020). Sustainable aquaculture requires environmental‐friendly treatment strategies for fish diseases. Reviews in Aquaculture, 12(2), 943-965.
Mallik, S. K., Shahi, N., Das, P., Pandey, N. N., Haldar, R. S., Kumar, B. S., & Chandra, S. (2015). Occurrence of Ichthyophthirius multifiliis (White spot) infection in snow trout, Schizothorax richardsonii (Gray) and its treatment trial in control condition. Indian Journal of Animal Research, 49(2), 227-230.
Persson, B. D., Aspán, A., Bass, D., & Axén, C. (2022). A case study of Dermotheca gasterostei (= Dermocystidium gasterostei, Elkan) isolated from three-spined stickleback (Gasterosteus aculeatus) captured in lake Vättern, Sweden. Bulletin of the European Association of Fish Pathologists.
Rahmati-Holasoo, H., Shokrpoor, S., Mousavi, H. E., & Ardeshiri, M. (2015). Concurrence of inverted-papilloma and papilloma in a gold spot pleco (Pterygoplichthys joselimaianus Weber, 1991). Journal of Applied Ichthyology, 31(3), 533-535.
Rowland, S. J., Mifsud, C., Nixon, M., Read, P., & Landos, M. (2008). Use of formalin and copper to control ichthyophthiriosis in the Australian freshwater fish silver perch (Bidyanus bidyanus Mitchell). Aquaculture research, 40(1), 44-54.
Schlenk, D., Gollon, J. L., & Griffin, B. R. (1998). Efficacy of copper sulfate for the treatment of ichthyophthiriasis in channel catfish. Journal of Aquatic Animal Health, 10(4), 390-396.
Sudhagar, A., Sundar Raj, N., Mohandas, S. P., Serin, S., Sibi, K. K., Sanil, N. K., & Raja Swaminathan, T. (2022). Outbreak of Parasitic Dinoflagellate Piscinoodinium sp. Infection in an Endangered Fish from India: Arulius Barb (Dawkinsia arulius). Pathogens, 11(11), 1350.
Tarján, Z. L., Doszpoly, A., Eszterbauer, E., & Benkő, M. (2022). Partial genetic characterisation of a novel alloherpesvirus detected by PCR in a farmed wels catfish (Silurus glanis). Acta Veterinaria Hungarica, 70(4), 321-327.
Valladao, G. M. R., Levy-Pereira, N., Viadanna, P. H. D. O., Gallani, S. U., Farias, T. H. V., & Pilarski, F. (2015). Haematology and histopathology of Nile tilapia parasitised by Epistylis sp., an emerging pathogen in South America. Bulletin of the European Association of Fish Pathologists, 35(1), 14-20.
Yang, C. W., Chang, Y. T., Hsieh, C. Y., & Chang, B. V. (2021). Effects of malachite green on the microbiomes of milkfish culture ponds. Water, 13(4), 411.
Yang, H., Tu, X., Xiao, J., Hu, J., & Gu, Z. (2023). Investigations on white spot disease reveal high genetic diversity of the fish parasite, Ichthyophthirius multifiliis (Fouquet, 1876) in China. Aquaculture, 562, 738804.
Wang, Z., Zhou, T., Guo, Q., & Gu, Z. (2017). Description of a new freshwater ciliate Epistylis wuhanensis n. sp.(Ciliophora, Peritrichia) from China, with a focus on phylogenetic relationships within family Epistylididae. Journal of Eukaryotic Microbiology, 64(3), 394-406.
Wu, T., Li, Y., Zhang, T., Hou, J., Mu, C., Warren, A., & Lu, B. (2021). Morphology and molecular phylogeny of three Epistylis species found in freshwater habitats in China, including the description of E. foissneri n. sp.(Ciliophora, Peritrichia). European Journal of Protistology, 78, 125767.
Žák, J., Roy, K., Dyková, I., Mráz, J., & Reichard, M. (2022). Starter feed for carnivorous species as a practical replacement of bloodworms for a vertebrate model organism in ageing, the turquoise killifish Nothobranchius furzeri. Journal of Fish Biology, 100(4), 894-908.
Like any other organism fishes can host pathogens and contract diseases, unlike many other pet related hobbies we are dealing with a wide diversity of different species. The diseases of aquarium fishes is there for a vast topic.
As my specialty is in the evolutionary biology of fishes, diseases are not my specialty. That is not to say like any other fish biologist I do not encounter them, given I am often not using high magnifications I actually am more familiar with larger ectoparasites then bacteria or protozoa. I do have a background in taxonomy as well so am familiar with understanding how even these bacteria, protozoa, fungi etc. are diagnosed to a degree.
Previously there have been many brilliant aquarium books focused on disease and I think more then anything I recommend an aquarist to have at least one. These books were often written by those with a background in pathology, included images of microscope slides and based in science.
Books I’d recommend (there will be others I have forgotten):
Discus Health, TFH Publication by Dieter Untergasser
Handbook of Fish Diseases, TFH Publication by Dieter Untergasser.
The Interpet Manual of Fish Health: Everything You Need to Know About Aquarium Fish, Their Environment and Disease Prevention, Firefly Books Ltd by Dr. Chris Andrews, Adrian Excell and Dr Neville Carrington.
The Practical Guide to Fish Diseases by Dr. Gerald Bassleer
The main issue with disease is to take anything also marketing a product with a pinch of salt unless it’s discussing a general compound e.g. malachite green, formaldehyde etc.
Diseases of aquarium fishes has become one of the most hotly contested topics within the aquarium hobby of recent years. With many websites making unfounded claims that lack citations where maybe they should to backup any novel ideas or information. This makes diagnosing disease for the general fishkeeper rather challenging. I hope I can make it a little easier or give areas to start researching.
This topic will cover multiple articles and therefore this contents should help guide a user through this page and others.
One of the biggest factors when it comes to any organism of preventing disease is ensuring the organism is healthy. There are several influences that might mean a fish is stressed enough to become more susceptible to disease; behavioral, environmental and also diet. If an organism is stressed then the immune system might not be functioning as well as it could and will be less able to fend of disease, this isn’t something new. Some disease might additionally be directly caused by these factors rather then by external pathogens.
So, lets explore preventative care.
Preventing disease by understanding specific fish behavior.
This is probably the most difficult to identify and sometimes the most difficult to cater for as we know so little about fish behavior. Here there are probably two outcomes of not catering for a fishes behavior; poor physiological health or abnormal behavior.
Poor physiological health is very obvious, a fish might have tattered fins, lost scales and reduced colouration. It could be that the fish is being directly attacked in territorial aggression or from a more predatory tankmate. In some fishes just simply removing an offending individual might solve the issue but with some fishes such as the Aulonocara (peacock cichlids), mbuna (multiple genera), Haplochromis etc. of the Rift valley this can create instability in the social hierarchy of the group (Piefke et al., 2021). Of course removing some worst offending species would maybe be a benefit and therefore considering what species are to be included to start off. These voids in hierarchy can create more aggression as individuals are additionally are then identifying where they all fit. It’s a common assumption to assume aggression is male focused, as I discuss in a previous article females do frequently display aggression (Female Aggression).
Aggression can just be simply territorial, Neolamprologous cichlids can be good examples of this where individuals will maintain a space and the location based often on maintaining resources reproductive, predator protection and dietary. Fish sociality can be so very complex so it’s not entirely simple (Walter et al., 1994). This territoriality can also be seen in many Loricariids (Plecos) but also Anabantoids such as Channa or gourami’s, not always related to reproduction but just defense of a space.
Even many shoaling species might show aggression and therefore in that context a good number with an appropriate sex ratio would be best. Sociality in many species is important though, even if it is fleeting there is a behavioral enrichment, this isn’t always possible. But for shoaling and schooling species having others of the same species or population is important.
Many popular fishes can be counted as some what shoaling or schooling such as clown loaches, Chromobotia macracanthus to neon tetra, Paracheirodon innesi. These fishes alone or even in small numbers such as 3 or 6 depending on the species you might see abnormal behavior. Sometimes difficult to identify as some species are just illusive. A shoaling species kept alone could be illusive, swim erratically around the glass or even maybe shoaling with a different species. It’s definitely very context dependent. Sociality is important for behavioral and maybe even physiological development (Riley et al., 2018), we know that though from other verebtrates……. The understanding of species can be difficult but realistically multiple individuals of different species would not make up a shoal. Whether it be Corydoras or tetra, these species might not be closely related but even if they are it doesn’t mean they can communicate and therefore benefit socially. In other fishes such as discus communication is so much in their coloration given they can recognize individuals (Satoh et al., 2016), many varieties have lost or altered this ability and could result in communication issues between domestics, wilds and certain varieties. This means it’s highly likely discus can identify the different species and even populations. I have experienced this myself. Just by the fact so many fishes of the same genus or group are located together behavior likely results in this speciation.
Tankmates themselves can provide another kind of harm, they could be eaten and vice versa. Generally avoiding tankmates that will fit in the mouth is a good rule of measure. Some fishes can expand their mouth further then expected and while many are gape limited (limited by the size of their mouth) others this limitation is minor. Even the slowest fish are more then capable of eating faster fishes, discus feeding on cardinal/neon tetra is commonly accounted and goldfish frequently feed on smaller tankmates. The biggest risk here is if the smaller fish is too big to be swallowed down and that larger fish chokes.
Goldfish, Carassius aureatus choking on an Otocinclus sp. the catfish had been housed with the goldfish for 2 years before this situation. Photo used with permission from the owner and the Facebook group: Goldfish Care.
The effect of the environment on fish disease.
More then often we think of the environment as purely about water parameters in fishes but the actual décor is important as well. I have been a long standing admin of goldfish groups and frequently seen where they have choked on gravel for example.
This is so diverse as so much can effect a fishes health.
Water parameters
The influence of water parameters on the health of fishes is so complex and so diverse, here I wont discuss hardness I have discussed it partially in the article on pH and hardness (here). Associated with mismanagement of hardness is gas bubble disease of which would require it’s own article or discussion, it is likely confused with a pH crash due to how quickly it occurs.
So, the main parameters we will focus on will be those related to nitrogen; ammonia, nitrites and nitrates. The values which cause death will vary depending on the fish and other parameters, many effects might seem asymptomatic unless a dissection is undertaken so do not assume because you cannot see an effect the fish isn’t affected. Ammonia itself burns the gills (Liu et al., 2021) but largely targets the the brain (Ip & Chew et al., 2010). Nitrite is the most well known as crossing into the blood combining with the blood to form methaemoglobin resulting in less oxygen carried around the body (Ciji & Akhtar, 2020), it can kill particularly rapidly seeming like a crash. These all are managed by a stable and cycled aquarium. Nitrate is maybe the least understood and the least studied as most studies focus on fishes with particular adaptability. This compound functions the same way as nitrites by combining with the blood to reduce oxygen saturation within the blood at higher volumes (Camargo et al., 2005). Many websites and a number of Youtubers focus on whether it kills but it shouldn’t be about rapid deaths rather long term effects, this is likely due to promoting methods where high nitrates are inevitable (Hrubec et al., 1996). So the question about low volumes becomes difficult, this is because most studies are short term and on fishes completely different from what we keep but even Hrubec et al. (1996) displays the toxicity of nitrate. It is better to assume toxicity then not just for the sake of water changes and half an hour or few hours a week, after all no one would argue for mammals to be left in their own waste because of intensive farming methods that do so.
Most of these nitrogen based compounds effect how oxygen is taken up whether it’s from burning the gills or the binding to the blood. So increasing oxygenation will not be harmful, methylene blue in small volumes is associated with increasing oxygen saturation in humans although it is difficult to find any research into the topic. Olufayo and Yusuf (2016) suggested that volumes of 67ppm to 199ppm of methylene blue didn’t increase oxygen saturation but previous research lists methylene blue as decreasing the solubility of oxygen (Khan et al., 2022). One aspect could be that largely when used in medicine it’s in humans and direct in the body, for fishes it’s added into the water so I think there is a whole other level of things at play. Another aspect of treating any higher values of these compounds is the use of Seachem prime, yes it does but decrease oxygen saturation so there is a balance (Seachem’s website).
Substrate
One of the things that least comes to mind when it comes to the health of fishes is substrates, there is so much diversity of them in stores and this can be overwhelming. Some might interact with the water parameters which is not usually ideal for many fishes as the focus of these is on plants.
The biggest risk substrate is gravels with any fish that might dig around in the substrate. It is frequently accounted particularly with goldfish where the gravel becomes stuck in either the oral or pharyngeal jaws of the fish.
Some of many situations where goldfish have choked on goldfish, used with permission of the owners and the facebook group: Goldfish Care.
Just as seriously from gravel is impaction although I have never encountered a certain case myself, if that gravel enters the digestive tract it wont exit easily unlike sand of which many fishes pass through their gut even in larger amounts harmlessly (Lujan et al., 2012).
Substrates offer an enrichment for so many fishes which is very important to recognise as so many species naturally search for food. I would rarely have a tank without it. The safest and most natural for many species is sands. One of these fishes that benefits so much are Corydoras and a number of loaches. Sharp substrates in these fishes is associated with erosion of the barbels present around the mouth although there is no studies on the topic and it is sometimes associated with the bacteria that gravel traps. This erosion leaves open wounds and an area highly open to infection.
Corydoras sterbai with erosion of the barbels caused by the sharp gravel and substrate. Image sourced from Aquarium Coop Forum, CARE and the user BMBSAD.
décor
This is probably the most logical but in the stress of setting up a tank it can be a bit overwhelming to decide what to get. Generally consider if you are having any secretive fishes they will need plenty of spaces to hide in a variety of shapes and sizes, being exposed can be stressful for them and you’ll see the stress patterning on them. When it comes to these fishes always be sure there isn’t decor that the fish can get stuck on, this seems more of an issue with artificial décor then natural.
Sharp décor can also cause wounds whether it be the metal rods in silk plants or sharp dragon rock, for many fishes this is no issue but for clumsy species or some bottom dwellers accidents happen. Some species which might have very rough spawning or aggressive behaviour then they can bash against décor so maybe avoiding anything too rough here but we shouldn’t exchange enrichment to almost bubble wrap our fishes.
Some items might have a risk if eaten, I am not sure how true this is but some people do record rasping fishes such as Loricariids feeding on the paint of some artificial décor. This is probably best avoided just because of the potential chemicals. Similar any decor from plastics you are not familiar with and might degrade in the water releasing microplastics or other compounds.
Conclusion
Obviously for preventative care there is so much more that needs to be considered. Think about the habitats these fishes experience in the wild. Observe your fishes and their behaviour, sometimes it’s worth doing so from a distance so they aren’t expecting food either that or a camera to see them at night. Some behaviour is not always seen.
What are pathogens?
Pathogens are organisms that cause disease. These in fishes can be as followed:
Viruses: Debatable if they are alive and therefore an organism. These cannot therefore do not have any treatment against them beyond keeping the immune system at it’s best and preventative care. Some viruses cannot be ‘cured’ and will always exist within the fish and some the fishes immune system will kill. Some viruses are fatal to the fish and others are not.
Bacteria: This is a massive group of organisms. Unlike viruses and like all the other groups I will later list not all are pathogens or parasites, many have different roles. These can be killed by a variety of treatments and by the fishes immune system.
Protozoa: This is a paraphyletic group of random organisms, not all are parasitic and some can be particularly difficult to treat while others much easier. A huge diversity of organisms.
Annelid/worms: Very few are ever seen in the aquarium other then leeches, these are true worms and more tricky to treat.
Nematodes: Similar to worms but not closely related at all. These are most often known for inhabiting the digestive tract or tissues in cysts. Many different wormers target this group.
Copepods, isopods: Easier to see in most situations and best removed by hand if spotted, these larger Arthropod invertebrates can be difficult to treat once becoming an infestation. The only ones a fishkeeper will usually encounter is fish lice, Argulus sp.
Algaes: The least obvious group to be parasitic/pathogenic but many are, velvet (Oodinium spp.) and related species with similar symptoms are reasonably common. This includes Cyanobacteria which are still algaes (Yanong et al., 2002). Technically as quite a lot of algae’s are protozoan and similar treatments sometimes work.
Disease and pathogen specificity.
Diseases and pathogens can be specific to certain groups of fishes or sometimes certain age demographics. A great example is some herpes type viruses many of which are specific to certain species or families (Hanson et al., 2011). This does mean if one fish has such a virus it wont be contracted by other taxa. You will also not find any confirmed cases of some diseases/pathogens in some fishes e.g. lymphocystis in carp and catfishes.
This is likely due to a diversity of different physiology between species, genera and even further families and more. Biology in general can differ so much certain groups might prevent access to certain taxa or they might lack the target organs and tissues.
Some individuals might be asymptomatic to certain diseases and pathogens.
Notes on Antibiotics
Antibiotic resistance is listed as one of the largest threats to humanity by the World Health Organisation, CDC etc. Bacteria and other pathogens are capable of resistance to a treatment on frequent exposure but bacteria being the most threatening. This has lead to many countries restricting their use, in countries like the UK they are only legal via prescription. Antibiotics unrestricted are commonly used without considering if the pathogen is actually a bacteria, if it is not it’ll have no effect but likely result in resistance of any bacteria around that are not currently a pathogen resulting in disease. In the aquarium there are many other treatments to try first. Antibiotics are reasonably specific to certain bacteria so would require knowing which are being targeted. If antibiotics are required then visit your vet, there are many fish vets within the UK who can be consulted on their opinion of the pathogen and course of treatment.
Pathogens of fishes and relevant articles to aid in diagnosis:
Discolouration and change in skin/scale condition (Unfinished)
Abnormal external bodies (Unfinished)
References
Camargo, J. A., Alonso, A., & Salamanca, A. (2005). Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates. Chemosphere, 58(9), 1255-1267.
Ciji, A., & Akhtar, M. S. (2020). Nitrite implications and its management strategies in aquaculture: A review. Reviews in Aquaculture, 12(2), 878-908.
Hanson, L., Dishon, A., & Kotler, M. (2011). Herpesviruses that infect fish. Viruses, 3(11), 2160-2191.
Hrubec, T. C., Smith, S. A., & Robertson, J. L. (1996). Nitrate toxicity: a potential problem of recirculating systems. Aquacultural Engineering Society Proceedings II: Successes and Failures in Commercial Recirculating Aquaculture. Northeast Regional Agricultural Engineering Service Cooperative Extension, Ithaca, NY.
Ip, Y. K., & Chew, S. F. (2010). Ammonia production, excretion, toxicity, and defense in fish: a review. Frontiers in physiology, 1, 134.
Khan, I., Saeed, K., Zekker, I., Zhang, B., Hendi, A. H., Ahmad, A., … & Khan, I. (2022). Review on methylene blue: Its properties, uses, toxicity and
Liu, M. J., Guo, H. Y., Liu, B., Zhu, K. C., Guo, L., Liu, B. S., … & Zhang, D. C. (2021). Gill oxidative damage caused by acute ammonia stress was reduced through the HIF-1α/NF-κb signaling pathway in golden pompano (Trachinotus ovatus). Ecotoxicology and Environmental Safety, 222, 112504.photodegradation. Water, 14(2), 242.
Lujan, N. K., Winemiller, K. O., & Armbruster, J. W. (2012). Trophic diversity in the evolution and community assembly of loricariid catfishes. BMC Evolutionary Biology, 12(1), 1-13.
Olufayo, M. O., & Yusuf, H. O. (2016). Toxicity of methylene blue on nile tilapia (Oreochromis Niloticus) juveniles. IOSR Journal of Environmental Science, Toxicology and Food Technology, 10, 9-16.
Piefke, T. J., Bonnell, T. R., DeOliveira, G. M., Border, S. E., & Dijkstra, P. D. (2021). Social network stability is impacted by removing a dominant male in replicate dominance hierarchies of a cichlid fish. Animal Behaviour, 175, 7-20.
Riley, R. J., Roe, T., Gillie, E. R., Boogert, N. J., & Manica, A. (2018). The development of social interactions in Corydoras aeneus larvae. bioRxiv, 455188.
Satoh, S., Tanaka, H., & Kohda, M. (2016). Facial recognition in a discus fish (Cichlidae): experimental approach using digital models. PloS one, 11(5), e0154543.
Walter, B., & Trillmich, F. (1994). Female aggression and male peace-keeping in a cichlid fish harem: conflict between and within the sexes in Lamprologus ocellatus. Behavioral Ecology and Sociobiology, 34, 105-112.
Yanong, R. P., Francis-Floyd, R., Curtis, E., Klinger, R. E., Cichra, M. F., & Berzins, I. K. (2002). Algal dermatitis in cichlids. Journal of the American Veterinary Medical Association, 220(9), 1353-1358.
When looking at food and diets we are often confronted with numerous ingredients with listed health benefits, it can be very confusing and difficult to understand. What adds to the complexity is the number of ingredients that can be added.
Like humans, fishes have nutritional requirements that’ll vary by species and even as the fish ages. These vitamins (Fig 2; Delbert, 2010) and minerals (Chanda et al., 2015) have various purposes.
Figure 2: Various nutritional factors and their benefits for fishes sourced from (Delbert, 2010): Delbert, M. G. I. (2010). Principles of fish nutrition. SRAC Publication, USA, 5003, 1-7.
This articles focus is not about catering for these vitamins and minerals particularly as a solid round diet; pellets, wafers and gel foods should cater for the basics of these. There is certainly an issue with many studies being species specific and focus on those used in aquaculture with a shorter term aim then ornamental fishes (Vucko et al., 2017). Previous studies have inferred that these aquaculture focused diets do fall short in terms of long term health (Žák et al., 2022), that is a whole other discussion.
Here our focus in those additional ingredients that might seem as strange but others are common herbs. This is not just about herbs or ingredients but what you could add to a gel diet.
Globe eye fancy goldfish, Carassius aureatus
I should quickly state that with a gel diet it’s quite easy to add ingredients that might make a diet cater better for a certain fish, gelling agent allowing. So for algivorous Loricariids I will add those extra algal powders to bulk out that element which meets their nutritional requirements (Vucko et al., 2017). It also would effect how long the product stores for once made into a gel so that should be considered.
Cellulose
This is a common additive due to the myth that Loricariids feed on wood, it has no nutritional or digestive benefit (Lujan et al., 2011). So of all the ingredients this is one I’d skip in regards to waste and feeding more.
Turmeric
This is a richly coloured member of the Zingiberaceae, Ginger family. It is described as being anti-inflammatory, antimicrobial etc. with many benefits for various organ systems but regardless of this it has limited availability for biological use as quickly removed from the system. This likely is influenced by how this root is added although being listed as hydrophobic and lipophobic makes uptake more difficult (Alagawany et al., 2021;
This is a richly coloured member of the Zingiberaceae, Ginger family. It is described as being anti-inflammatory, antimicrobial etc. with many benefits for various organ systems but regardless of this it has limited availability for biological use as quickly removed from the system. This likely is influenced by how this root is added although being listed as hydrophobic and lipophobic makes uptake more difficult (Alagawany et al., 2021; Fagnon et al., 2020).
One of the biggest concerns with adding in any additional elements to a diet is whether the product is toxic or not, luckily in terms of turmeric it is non-toxic although might have small effects on the gills. (de Moraes França Ferreira et al., 2017). Although there is a concern at higher volumes which depend on the individual species (Fagnon et al., 2020).
Basil
One of the herbs that is most easily accessable in so many different forms and even easy to grow. Much like expected basil is not just very palatable for fishes but also easily digested in an experiment on tilapia and sea bream. Benefits also included an improved growth rate (El-Dakar et al., 2008; El-Dakar et al., 2015). Most studies on this herb in regards to relevance as hobbyists seems to focus on their use aquaponically, as an ingredient is understandable for it’s lack of research and use as per a gram it’s not a cheap plant to use.
Paprika
For a better price and accessibility Paprika should be more of a popular ingredient as can easily be bought in bulk. The benefits of paprika are obvious given it contains many carotenoids (Maeda et al., 2021). These carotenoids are important for any red colourations in fishes (Hancz et al., 2003) with other health benefits (Amiruddin et al., 2021)
Seeds
Seeds are an interesting addition and certainly not for all fishes but there is evidence to suggest a diversity of aquarium fishes would feed on seeds in the wild (Weiss et al., 2016). One of these being Hypancistrus inspector (Armbruster, 2002). Although it is some what difficult to judge if these seeds are processed and to what extent. Due to seed dispersal by fishes it is highly likely that many seeds aren’t processed by a variety of fishes (Pollux, 2011) but those Hypancistrus do seem to be breaking them apart (Armbruster, 2002).
Rather then ingredients the aim is to give a starting point for further research. It might be worth exploring a wider range of ingredients and addition to a fishes diet. While there might not always be the research to back it up if it is safe then there is many benefits to the hobby by experimentation.
References:
Alagawany, M., Farag, M. R., Abdelnour, S. A., Dawood, M. A., Elnesr, S. S., & Dhama, K. (2021). Curcumin and its different forms: A review on fish nutrition. Aquaculture, 532, 736030.
H Amiruddin, M., Norhalis, M. F., Sumarwati, S., & Rashid, Y. N. (2021). Dietary effect of red paprika used to enhance the coloration of red tilapia (oreochromis niloticus). Journal of Aquaculture and Fish Health, 10(1), 25-33.
Armbruster, J. W. (2002). Hypancistrus inspector: a new species of suckermouth armored catfish (Loricariidae: Ancistrinae). Copeia, 2002(1), 86-92.
Chanda, S., Paul, B. N., Ghosh, K., & Giri, S. S. (2015). Dietary essentiality of trace minerals in aquaculture-A Review. Agricultural Reviews, 36(2), 100-112.
Delbert, M. G. I. (2010). Principles of fish nutrition. SRAC Publication, USA, 5003, 1-7.
El-Dakar, A., Hassanien, G., Gad, S., & Sakr, S. (2008). Use of dried basil leaves as a feeding attractant for hybrid tilapia, Oreochromis niloticus X Oreochromis aureus, fingerlings. Mediterranean Aquaculture Journal, 1(1), 35-44.
El-Dakar, A. Y., Shalaby, S. M., Nemetallah, B. R., Saleh, N. E., Sakr, E. M., & Toutou, M. M. (2015). Possibility of using basil (Ocimum basilicum) supplementation in gilthead sea bream (Sparus aurata) diet. Egyptian Journal of Aquatic Research (Online), 41(1).
Fagnon, M. S., Thorin, C., & Calvez, S. (2020). Meta‐analysis of dietary supplementation effect of turmeric and curcumin on growth performance in fish. Reviews in Aquaculture, 12(4), 2268-2283.
Hancz, C., Magyary, I., Molnar, T., Sato, S., Horn, P., & Taniguchi, N. (2003). Evaluation of color intensity enhanced by paprika as feed additive in goldfish and koi carp using computer‐assisted image analysis. Fisheries science, 69(6), 1158-1161.
Lujan, N. K., German, D. P., & Winemiller, K. O. (2011). Do wood‐grazing fishes partition their niche?: morphological and isotopic evidence for trophic segregation in Neotropical Loricariidae. Functional Ecology, 25(6), 1327-1338.
Maeda, H., Nishino, A., & Maoka, T. (2021). Biological activities of paprika carotenoids, capsanthin and capsorubin. Carotenoids: Biosynthetic and biofunctional approaches, 285-293.
de Moraes França Ferreira, P., Condessa, S. S., Rocha, J. S., Caldas, D. W., Gomes, J. R., Soares, M. T., … & Zuanon, J. A. S. (2017). Is the use of turmeric in the diet safe for fish?. Aquaculture Research, 48(9), 4623-4631.
Pollux, B. J. A. (2011). The experimental study of seed dispersal by fish (ichthyochory). Freshwater Biology, 56(2), 197-212.
Vucko, M. J., Cole, A. J., Moorhead, J. A., Pit, J., & de Nys, R. (2017). The freshwater macroalga Oedogonium intermedium can meet the nutritional requirements of the herbivorous fish Ancistrus cirrhosus. Algal research, 27, 21-31.
Weiss, B., Zuanon, J. A., & Piedade, M. T. (2016). Viability of seeds consumed by fishes in a lowland forest in the Brazilian Central Amazon. Tropical Conservation Science, 9(4), 1940082916676129.
Žák, J., Roy, K., Dyková, I., Mráz, J., & Reichard, M. (2022). Starter feed for carnivorous species as a practical replacement of bloodworms for a vertebrate model organism in ageing, the turquoise killifish Nothobranchius furzeri. Journal of Fish Biology, 100(4), 894-908.
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