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An Algae eating loach, the Hillstream loaches, Balitoridae & Gastromyzontidae: Dietary Ecology

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While my fascination is largely with Loricariids, rasping species are interesting. Unlike the majority of fishes who are limited in what they can eat by the size of their mouth rasping fishes are not and yet ecologically seem very misunderstood. It’s also no lie that I have a soft spot for loaches and have kept quite the diversity of different species.

Sewellia breviventralis

Balitoridae are those dorsio-ventrally flattened loaches from the group Cypriniformes, often referred to the superfamily Cobitoidea. So while Balitoridae are commonly confused with pleco’s, Loricariids they are actually more closely related to carp, barbs and minnows.

Phylogeny of loaches, Cobitoidea from: Wang, Y., Shen, Y., Feng, C., Zhao, K., Song, Z., Zhang, Y., … & He, S. (2016). Mitogenomic perspectives on the origin of Tibetan loaches and their adaptation to high altitude. Scientific reports, 6(1), 29690.

There are many genera we keep under this group in the trade, the most common being Sewellia lineaolata but otherwise followed by a variety of species from the genera Pseudogastromyzon and Gastromyzon. Occasionally other genera appear but as by catch many other Sewellia come into the trade such as SEW001 and S. breviventralis. If you want a rare fish and can do some research, it’s not difficult to find something rare or unusual in this group.

Not all have this extreme suction cup-like morphology, some are much more elongate.

The Habitats

As the name suggests these fishes seem to be highly riverine, rocks and high velocity water. There is little to no botanicals, wood and certainly no plants but this clear water (Randall et al., 2023) is where algae can thrive where plants cannot compete. These fishes thrive in a habitat more similar to some Ancistrus, Chaetostoma or Astroblepus would in South America.

Balitoridae Diets

Balitoridae no doubt shows likely a wide range of diets, there doesn’t seem to be the research on them. While few studies exist of these fishes diets the evidence suggests the genus Pseudogastromyzon feeds largely on algaes, both cyanobacteria and traditional Chlorophytic algaes (Fig 1; Yang & Dudgeon, 2010).

Figure 1: Pseudogastromyzon myersi stomach contents from: Yang, G. Y., & Dudgeon, D. (2010). Dietary variation and food selection by an algivorous loach (Pseudogastromyzon myersi: Balitoridae) in Hong Kong streams. Marine and Freshwater Research, 61(1), 49-56.

Although a later study inferred Pseudogastromyzon myersi feeds on 60-100% of their diet is algaes, with a lot of diversity. In comparison another genus with a similar body morphology, Liniparhomaloptera while feeding on largely algae’s displayed a diet of largely 6-20% invertebrates (Mantel et al., 2004). This is also displayed in Homaloptera sp. which feeds on around 13-14% insects, although the majority of their diet is detritus (Fuadi et al., 2016). As discussed before detritus is a vague classification and could realistically mean anything, it is most likely ‘bacteria’ over waste. A large amount of invertebrates consumed by Homaloptera is ostracods and aquatic larvae, it seems that they feed on minimal algae’s (Nithirojpakdee et al., 2014).

The most unusual thing seems to be this is the only study on the diet of Balitoridae, the majority of studies as with other groups has focused in their phylogenetics and taxonomy (Yang, 2008).

Liniparhomaloptera disparis, by  H.T.Cheng https://www.inaturalist.org/observations?user_id=oryzias

The Dietary Morphology

Surprisingly here we have a really good comparison of morphology just externally, compare Gastromyzon, Sewellia etc. with Liniparhomaloptera and immediately their head is much wider. We can some what assume a wider head correlates with a wider jaw and wider jaws, more numerous teeth correlates with a more algivorous diet (Lujan & Armbruster et al., 2012). If we look at the ventral morphology of these fishes one has much wider jaws then the other, Pseudogastromyzon has comparatively wider jaws and general head size then Liniparhomaloptera but is still wider then Homaloptera. The two former species, similar to Sewellia display jaws more similar to Loricariids, plate like jaws with numerous teeth.

Gastromyzon on the left, Sewellia on the right. Image source from: Willis, J., Burt de Perera, T., Newport, C., Poncelet, G., Sturrock, C. J., & Thomas, A. (2019). The structure and function of the sucker systems of hill stream loaches. bioRxiv, 851

There is some obvious jaw diversity in Balitoridae, the mouth of Gastromyzon is much wider then the curved mouth of Sewellia (Willis et al., 2019). I can assume that Gastromyzon is much more similar to Pseudogastromyzon ecologically and regarding diet although they are not closely related (Shao et al., 2020). There is no doubt either species probably feeds on a large amount of algae and other microbial films, but without any ecological records we can only assume.

The shape of the jaw isn’t just about taking up the food but can also be related to being able to extract that food item, while wide, those curved jaws could infer a niche involving extracting microbes from the cracks in rocks and between rocks. Although these cracks, fishers etc. are unlikely to have as many of these microbial films compared to where invertebrates might find refuge. There could be a rugosity aspect as if that habitat has rocks that are naturally bumpy it makes sense to have those more curved jaws then a long jaw which could be unable to access some of these films. A bit like a hoover, you have one part for large flat areas and another to deal with areas that aren’t so flat.

Unlike Loricariids I do not feel looking at their jaws they quite share the exact same niche as they seem to lack the same morphology. Perhaps this is exclusive to siluriformes and there are rasping catfishes in Africa and Asia.

The mouth of Pseudogastromyzon fasciatus as featured in: Chen, J., Chen, Y., Tang, W., Lei, H., Yang, J., & Song, X. (2023). Resolving phylogenetic relationships and taxonomic revision in the Pseudogastromyzon (Cypriniformes, Gastromyzonidae) genus: molecular and morphological evidence for a new genus, Labigastromyzon. Integrative Zoology.

Similar to Loricariids (Krings et al., 2023) it’s is likely not just about the skeletal anatomy that infers diet. The soft tissues at the mouth could play a role as displayed in Chen et al. (2023), there are many ridges on the mouth of the Pseudogastromyzon included these might play a role in sticking to surfaces in their high velocity environment but perhaps when feeding aid in the removal of algaes from a surface.

What should you feed hillstream loaches?

Regardless of the diversity of Balitoridae diets, the majority of their diet is still either detritus and/or algae’s. So I’d build up from that then maybe including a small range of frozen foods for them to forage for.

A brand like Repashy soilent green would be ideal, it is largely algaes with some invertebrates. Alternatively if you can find the algae based New Life Spectrum, AlgaeMax but a product under the same name is higher in fish meals. In the Bag Tropical Fishkeeping UK’s pleco pops would also be great.

It is really tricky to find diets that contain a reasonable volume of algae’s, even if they are listed as algae wafers. Vegetables and cereals do not make up nutritionally for algaes either. At the end of the day if you can’t get these diets then these fishes are not tricky to feed and making your own gel diet is possible, I will maybe write an article about that in future.

References:

Chen, J., Chen, Y., Tang, W., Lei, H., Yang, J., & Song, X. (2023). Resolving phylogenetic relationships and taxonomic revision in the Pseudogastromyzon (Cypriniformes, Gastromyzonidae) genus: molecular and morphological evidence for a new genus, Labigastromyzon. Integrative Zoology.

Fuadi, Z., Naira, K. B., & Hasri, I. 2016. HABITS EATING FISH OF ILI (Homaloptera Sp.) PESTAK RIVER DISTRICT IN CENTRAL ACEH INDONESIA.

Krings, W., Konn-Vetterlein, D., Hausdorf, B., & Gorb, S. N. (2023). Holding in the stream: convergent evolution of suckermouth structures in Loricariidae (Siluriformes). Frontiers in Zoology, 20(1), 37.

Lujan, N. K., & Armbruster, J. W. (2012). Morphological and functional diversity of the mandible in suckermouth armored catfishes (Siluriformes: Loricariidae). Journal of Morphology, 273(1), 24-39.

Mantel, S. K., Salas, M., & Dudgeon, D. (2004). Foodweb structure in a tropical Asian forest stream. Journal of the North American Benthological Society, 23(4), 728-755.

Nithirojpakdee, P., Beamish, F. W. H., & Boonphakdee, T. (2014). Diet diversity among five co-existing fish species in a tropical river: integration of dietary and stable isotope data. Limnology, 15, 99-107.

Randall, Z. S., Somarriba, G. A., Tongnunui, S., & Page, L. M. (2023). Review of the spotted lizard loaches, Pseudohomaloptera (Cypriniformes: Balitoridae) with a re‐description of Pseudohomaloptera sexmaculata and description of a new species from Sumatra. Journal of Fish Biology, 102(1), 225-240.

Shao, L., Lin, Y., Kuang, T., & Zhou, L. (2020). Characterization of the complete mitochondrial genome of Balitora ludongensis (Teleost: Balitoridae) and its phylogenetic analysis. Mitochondrial DNA Part B, 5(3), 2308-2309.

Wang, Y., Shen, Y., Feng, C., Zhao, K., Song, Z., Zhang, Y., … & He, S. (2016). Mitogenomic perspectives on the origin of Tibetan loaches and their adaptation to high altitude. Scientific reports, 6(1), 29690.

Willis, J., Burt de Perera, T., Newport, C., Poncelet, G., Sturrock, C. J., & Thomas, A. (2019). The structure and function of the sucker systems of hill stream loaches. bioRxiv, 851592.

Yang, Y. (2008). The ecology of a herbivorous fish (Pseudogastromyzon myersi: balitoridae) and its influence on benthic algal dynamics in four HongKong streams. HKU Theses Online (HKUTO).

Yang, G. Y., & Dudgeon, D. (2010). Dietary variation and food selection by an algivorous loach (Pseudogastromyzon myersi: Balitoridae) in Hong Kong streams. Marine and Freshwater Research, 61(1), 49-56.

Pleco’s and Whiptail Catfishes, the Beginners Guide to Loricariid catfishes.

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With a whole section designated to Loricariidae, I haven’t actually done a beginners guide to the group. This website largely isn’t designed for beginners but Loricariid’s are some of the most misunderstood group of fishes.

  1. What is a Pleco or Whiptail Catfish?
  2. What is the L number system?
  3. Introduction
  4. The size of plecos
  5. What should I feed my pleco?
  6. Do pleco’s need wood?
  7. What parameters do pleco’s need?
  8. What decor do plecos require?
  9. Tankmates
  10. Recommended websites
  11. References:

What is a Pleco or Whiptail Catfish?

These two common names have no certain definitions, the majority of their use is a pick and mix that varies between the user. It is even more confusing that some loaches are referred to as pleco’s. All common names are equally as valid as each other. I find it easier to refer to the whole of Loricariidae as plecos, why? Figure 1 explains this situation. By excluding the subfamily Loricariinae (whiptail catfishes), you exclude Loricariichthys of which Plecostomus was synonymized with. If you exclude Hypoptopominae (Otocinclus and relatives) then Neoplecostomini and Neoplecostomus are excluded. Ancistrus, commonly known as bristlenose’s places right in the middle of Hypostominae, traditional plecos but Ancistrus also includes the medusa pleco, Ancistrus ranunculus. Then outside of all of these groups is Rhinelepinae, so that includes the pineapple pleco’s, and on it’s own Pseudancistrus genisetiger, so none of those are plecos then?

What would solve the common name issue? Simply not using them. Sadly with Loricariids you can’t avoid scientific names as many species do lack common names or share them.

Figure 1: Annotated phylogeny of Loricariidae from Roxo, F. F., Ochoa, L. E., Sabaj, M. H., Lujan, N. K., Covain, R., Silva, G. S., … & Oliveira, C. (2019). Phylogenomic reappraisal of the Neotropical catfish family Loricariidae (Teleostei: Siluriformes) using ultraconserved elements. Molecular phylogenetics and evolution, 135, 148-165.

What is the L number system?

The L number system is actually quite simple, it is a hobby made system originating from the German Magazine, DATZ. It simply designates an L number to a variant or species. It is commonly stated that undescribed species are given L numbers, this is partially true but there are many species who were described decades or over 100 years before given their L number such as the sailfin/common/leopard pleco, Pterygoplichthys gibbiceps who was described by Kner in 1854.

I am not entirely convinced the L number system is easy to use, the order of the numbers doesn’t infer anything regarding the fishes care or lineages. Multiple species can share an L number e.g. Baryancistrus demantoides and Hemiancistrus subvirdis are both L200 also known as green phantoms. Hemiancistrus subvirdis is likely the same species as L128 although that is a topic for another day. One species can have multiple L numbers, which don’t always describe populations or all of the morphological variation of the species e.g. Baryancistrus xanthellus has 4 L numbers.

To top it off there are fake L numbers, L600 for example described Pseudacanthicus leopardus who already has the L numbers, L114 and L427. The L number system is only up to around 530 species so far. The letters added to L numbers aren’t a part of the L number system and increase confusion. Sometimes species are given by the hobby the L number of an entirely different species such as L144 which doesn’t even exist in the hobby and hasn’t done for decades or L056 for Parancistrus aurantiacus when actually that L number refers to an undescribed brown Pseudancistrus.

There is additionally the LDA number system which does overlap slightly but isn’t so expansive.

Introduction

Loricariidae, pleco’s are the largest family within the order of fishes known as Siluriforme also known as catfishes or welse, representing 1050 currently described species (Fricke et al., 2024). This group is exclusive to South and Central American freshwaters although has invasive populations in many continents.

Panaque nirolineatus from Maidenhead Aquatics at Ascot.

The family is identified by a downwards (ventrally) facing oral disc shaped mouth, in some species this is more of a suction cup whereas others they cannot attach to surfaces well or at all. This trait isn’t exclusive to Loricariids but it is not quite the same in other groups. Further more, Loricariids are defined by having a body covered in bony scutes, more scientifically known as dermal plating, not scales as catfishes lack scales.

Baryancistrus chrysolomus.

Not does Loricariidae just have dermal plating but they have spines known as odontodes, external teeth (Fig 2). Sometimes these are sexually dimorphic but not always, they can also be shed seasonally.

Figure 2: Odontodes found on I believe Peckoltia sabaji.

Loricariids realistically are one of the most morphologically diverse clades of fishes.

This diversity means that as a group, Loricariids are really difficult if impossible to generalize, research is paramount for this group.

The size of plecos

As one of the most diverse groups of fishes their size varies vastly, 0.2-0.8cm in Parotocinclus halbothi (Lehmann et al., 2014) to 100cm SL possibly in Acanthicus adonis. There is a wide diversity of sizes within many groups so there is no shortage of smaller and larger species. At the end of the article I will recommend reliable websites, there is frequent misleading information about the adult size of many species.

It is important to recognize reliable websites will use standard length, from the head to the base of the caudal/tail fin. That caudal/tail fin will be excluded as these can vary in length. I mention this as many people will not consider this measurement and forget their fish grows much bigger then they would originally consider. This is explained in detail in this article.

Parancistrus aurantiacus

What should I feed my pleco?

This topic has the majority of misconceptions about Loricariids, the majority are algivores or detritivores (Lujan et al., 2012) but a wide range of diets are utilized. I have written a range of articles on a wide variety of diets across the family:  Hypancistrus (zebra, king tigers, queen arabesque, snowball pleco, L236 etc.), Panaque and Panaqolus (royal pleco’s, flash pleco and the clown pleco’s), substrate dwelling Loricariinae (Pseudohemiodon, Planiloricaria etc.), Baryancistrus (gold nugget pleco, mango/magnum pleco, snowball pleco), mollusc specialists (Scobinancistrus, goldie/sunshine pleco, vampire pleco, galaxy pleco, Leporacanthicus), Chaetostoma (Rubbernoses and one of the bulldog plecos) and finally algivores/detritivores.

There are a few myths regarding Loricariid diets I will summerise:

  • Pleco’s are largely carnivores, there are plenty of papers discussing their diets and while I wont cite them all Lujan et al. (2015) summerises it well.
  • Pleco’s become carnivorous with age, there isn’t any studies regarding change in diet as the fishes age. Unlike most fishes, the majority of Loricariids break down their food before it enters their mouth, so the size of the fish doesn’t limit their food item, so not gape limited. This means unlike many other fishes their food item doesn’t need to change with size.
  • Pleco’s clean a tank, while the majority are algivores and detritivores (Lujan et al., 2015) there is a wide diversity in niche partitioning (Lujan et al., 2011) and therefore those algivore’s specialize in certain algae’s. These algae’s seem not to be those that are an issue in the aquarium. Given their lifespan and waste production, they could be an expensive solution to high nutrients.
  • Pleco’s don’t eat cyanobacteria, they actually don’t just eat those that are pests in the aquarium, in the wild they feed on cyanobacteria (Valencia & Zamudio ,2007).

Always check the ingredients as some diets that claim to contain algae’s might contain anything from none to 5%.

Do pleco’s need wood?

This is discussed in more detail here: Panaque and Panaqolus (royal pleco’s, flash pleco and the clown pleco’s).

In simple NO, they do not need wood. The only species that utilize wood are in the genera Panaque, Panaqolus, Hypostomus cochliodon group, Pseudoqolus and perhaps Lasiancistrus heteracanthicus. These groups all share unique spoon shaped teeth they can gouge into wood and if found among wood, wood is found in their gut (Lujan et al., 2017). No other Loricariid has wood in their gut, I’ve scoured gut records but they simply don’t have the jaws or teeth to gouge into wood. There have been many studies to confirm these fishes do not eat/digest the wood (Watts et al., 2021; German, 2009), instead they are just evolved to feed on biofilms, like other species from where other species cannot access, within wood (Lujan et al., 2011).

Peckoltia compta

What parameters do pleco’s need?

While the general idea is that Loricariids and in general anything South America requires soft, low conductivity and acidic water there is a wide diversity of parameters. Some species are found in lower temperatures while other much higher, 28c or higher (Collins et al., 2015; Urbano‐Bonilla & Ballen et al., 2021). Other misconceptions are that South American habitats have a lot of leaf litter and is black water, this is completely untrue, there are many different habitat types (Bogotá-Gregory et al., 2020). In general the majority of Loricariidae are rheophilic and would benefit from a current within the aquarium although there is some diversity (Krings et al., 2023). In general any current within the aquarium is a lot weaker then any of the weaker streams in their wild range.

Planet Catfish has really accessible information to identify parameters before looking into the scientific literature.

What decor do plecos require?

This is largely the only consistent aspect of Loricariids. If anyone has kept Loricariids they will know how much they like cracks, crevices, hiding spaces, rocks, branches and in general cover. There are many caves and tunnels on the market designed for the preferences of a variety of species. I recommend stacking up wood or rocks in a careful way so nothing falls but this will create many more caves.

Tankmates

This will always be based on experience and understanding of the fishes. It’s important to recognize a few key things about Loricariids.

  • Loricariids do not often feed rapidly but even if they do it can take them minutes to an hour to reach food. Fast feeding fishes such as most cichlids, loaches, tetra, livebearers and goldfish particularly in large numbers are a bad idea.
  • Their temperature might not overlap.
  • They will need a current, some more then others which this means they wont work with fishes like long finned Betta splendens.
  • While some Loricariids feed on food items that they wouldn’t naturally it doesn’t mean it is good for them. Bloat can happen in some genera more then others. So I do not recommend keeping other fishes with Loricariids who you plan on feeding anything like beefheart.
  • Hardness, conductivity etc. We don’t actually know the KH or GH of the water many of these fishes come from, usually we have conductivity and pH records for many waters. Ideally these fishes are ill-suited regardless with Rift Valley cichlids, generally the biggest issue is above, those cichlids feed way too rapidly for any Loricariid.

Planet Catfish

Scotcat

Loricariidae.info

L-Welse

www.suedamerikafans.de

References:

Collins, R. A., Ribeiro, E. D., Machado, V. N., Hrbek, T., & Farias, I. P. (2015). A preliminary inventory of the catfishes of the lower Rio Nhamundá, Brazil (Ostariophysi, Siluriformes). Biodiversity Data Journal, (3).

Bogotá-Gregory, J. D., Lima, F. C., Correa, S. B., Silva-Oliveira, C., Jenkins, D. G., Ribeiro, F. R., … & Crampton, W. G. (2020). Biogeochemical water type influences community composition, species richness, and biomass in megadiverse Amazonian fish assemblages. Scientific Reports, 10(1), 15349.

Fricke, R., Eschmeyer, W. N. & Van der Laan, R. 2024.  ESCHMEYER’S CATALOG OF FISHES: GENERA, SPECIES, REFERENCES. (http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp). Electronic version accessed 22 July 2024.

German, D. P. (2009). Inside the guts of wood-eating catfishes: can they digest wood?. Journal of Comparative Physiology B, 179, 1011-1023.

Krings, W., Konn-Vetterlein, D., Hausdorf, B., & Gorb, S. N. (2023). Holding in the stream: convergent evolution of suckermouth structures in Loricariidae (Siluriformes). Frontiers in Zoology, 20(1), 37.

Lehmann, P. A., Lazzarotto, H., & Reis, R. E. (2014). Parotocinclus halbothi, a new species of small armored catfish (Loricariidae: Hypoptopomatinae), from the Trombetas and Marowijne River basins, in Brazil and Suriname. Neotropical Ichthyology, 12, 27-33.

Lujan, N. K., Cramer, C. A., Covain, R., Fisch-Muller, S., & López-Fernández, H. (2017). Multilocus molecular phylogeny of the ornamental wood-eating catfishes (Siluriformes, Loricariidae, Panaqolus and Panaque) reveals undescribed diversity and parapatric clades. Molecular phylogenetics and evolution, 109, 321-336.

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.

Roxo, F. F., Ochoa, L. E., Sabaj, M. H., Lujan, N. K., Covain, R., Silva, G. S., … & Oliveira, C. (2019). Phylogenomic reappraisal of the Neotropical catfish family Loricariidae (Teleostei: Siluriformes) using ultraconserved elements. Molecular phylogenetics and evolution, 135, 148-165.

Urbano‐Bonilla, A., & Ballen, G. A. (2021). A new species of Chaetostoma (Siluriformes: Loricariidae) from the Orinoco basin with comments on Amazonian species of the genus in Colombia. Journal of Fish Biology, 98(4), 1091-1104.

Valencia, César Román, and Héctor Zamudio. 2007. Dieta y reproducción de Lasiancistrus caucanus (Pisces: Loricariidae) en la cuenca del río La Vieja, Alto Cauca, Colombia. Revista del Museo Argentino de Ciencias Naturales nueva serie 9(2): 95-101.

Watts, J. E., McDonald, R. C., & Schreier, H. J. (2021). Wood degradation by Panaque nigrolineatus, a neotropical catfish: diversity and activity of gastrointestinal tract lignocellulolytic and nitrogen fixing communities. In Advances in Botanical Research (Vol. 99, pp. 209-238). Academic Press.

Bloodworm, a scape goat?

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Bloodworm has been a food that has been discouraged against for around 10 or more years. There has never been any doubt that many fishes feed on Chironomatid larvae in the wild (Delariva & Agostinho, 2001; Valtierra-Vega & Schmitter-Soto, 2000), even discus feed on them (Crampton, 2008). Chironomatid larvae being the more scientific name for bloodworm. You might have even seen these larvae in your pond, buckets or similar.

Bloodworms as featured in: Paice, R. (2016). Assessment of mosquito larvicide impacts on aquatic invertebrates in the Vasse-Wonnerup Wetland System.

So why are bloodworms so feared?

I don’t think there is a true origin to this, it is still one of the most common live and frozen foods used, it’s cheap and easy to find. Maybe there are still some aspects of when tubifex was feared due to sewage contamination.

Bloodworm being the larvae of an insect does have a casing, known as an exoskeleton formed of chitin. This can be difficult to digest and for some fishes impossible, although many species are possibly sold as bloodworm it’s likely there is some diversity. There are reports of constipation and similar caused by bloodworm, although bloating is tricky and can have many causes from bacterial infections to a food item not being processed.

Bloodworm is not the entire diet of any fishes I’ve researched and when fed as an entire diet it results in liver enlargement and and poorer body condition (Žák et al., 2022), these results are similar to Hao et al. (2021) where removing to a formulated diet increases general health of the fish.

I chose this topic to find reasons that I am wrong, that bloodworm is much better then I thought it was. It doesn’t seem bad for fattening up fishes but does seem to come with a variety of problems, as a result I think I will continue to recommend Tubifex.

The real worm to try

Tubifex is a relatively common live, frozen and freeze dried food available. Unlike bloodworm it’s an annelid, true worm and is fully aquatic. It lacks the thick chitin casing of bloodworms, making them much more easy to digest. To cultivate they are less tricky given their lifestyle but do need a constant flow of freshwater.

Tubifex as featured in: https://plantsam.com/

Unlike bloodworm, Tubifex was vilified for years, this amazing genus is extremely adaptable. This adaptability has meant that Tubifex can be found in the most hostile and polluted habitats and at one time this is where they were collected for the aquarium trade. Due to being collected from very polluted habitats it was not the most ideal live food to avoid pollution. Frozen will be another story as most are gamma irradiated, killing most bacteria on them. But for many years Tubifex is farmed in a clean and sustainable matter.

Unlike bloodworm Tubifex is very high in nutrition (Herawati et al., 2016) and has shown to increase growth when mixed with a prepared diet (Alam et al., 2021) even when compared to other live foods (Mellisa et al., 2018).

Human health

Bloodworm is a known allergen leading to asthma (Wu et al., 2005; Nandi et al., 2014). As someone who is not a medical practitioner I cannot offer much advice, allergies can occur at any time and it is good to be cautious. When dealing with bloodworm, handling particularly wearing disposable gloves can be a good idea, using a tub to defrost it in. It does beg the question given it is quite a common allergen whether to use it at all? In my experience I have met very few people who are allergic to bloodworm.

References:

Alam, M. A., Khan, M. A., Sarower-e-Mahfuj, M. D., Ara, Y., Parvez, I., & Amin, M. N. (2021). A model for tubificid worm (Tubifex tubifex) production and its effect on growth of three selected ornamental fish. Bangladesh Journal of Fisheries, 33(2), 205-214.

Crampton, W. G. (2008). Ecology and life history of an Amazon floodplain cichlid: the discus fish Symphysodon (Perciformes: Cichlidae). Neotropical Ichthyology, 6, 599-612.

Delariva, R. L., & Agostinho, A. A. (2001). Relationship between morphology and diets of six neotropical loricariids. Journal of Fish biology, 58(3), 832-847.

Hao, Q., Teame, T., Wu, X., Ding, Q., Ran, C., Yang, Y., … & Zhou, Z. (2021). Influence of diet shift from bloodworm to formulated feed on growth performance, gut microbiota structure and function in early juvenile stages of hybrid sturgeon (Acipenser baerii× Acipenser schrenckii). Aquaculture, 533, 736165.

Herawati, V. E., Nugroho, R. A., Hutabarat, J., & Karnaradjasa, O. (2016). Profile of amino acids, fatty acids, proximate composition and growth performance of Tubifex tubifex culture with different animal wastes and probiotic bacteria. Aquaculture, Aquarium, Conservation & Legislation, 9(3), 614-622.

Mellisa, S., Rahimi, S. A. E., & Umiati, U. (2018). The effect of different live feeds on the growth and survival of comet goldfish Carrasius auratus auratu larvae. In IOP Conference Series: Earth and Environmental Science (Vol. 216, No. 1, p. 012025). IOP Publishing.

Nandi, S., Aditya, G., Chowdhury, I., Das, A., & Saha, G. K. (2014). Chironomid midges as allergens: evidence from two species from West Bengal, Kolkata, India. Indian Journal of Medical Research, 139(6), 921-926.

Valtierra-Vega, M. T., & Schmitter-Soto, J. J. (2000). Feeding habits of cichlid species (Perciformes: Cichlidae) in Caobas lake, Quintana Roo, Mexico. Revista de Biologia Tropical, 48(2-3), 503-508.

Wu, K. C., Räsänen, K., & Hudson, T. J. (2005). Fishing for allergens: bloodworm-induced asthma. Allergy, Asthma & Clinical Immunology, 1, 1-2.

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.

Epistylis, misinformation in the aquarium hobby.

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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).

Figure 4: Credits to Aquarium Science https://aquariumscience.org/

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.

What to feed your pleco when they wont eat.

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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.

One day I will create a proper list of what Loricariid eats what as far as we know but currently I cannot. I do have articles on some commonly misunderstood fishes; Hypancistrus (zebra, king tigers, queen arabesque, snowball pleco, L236 etc.), Panaque and Panaqolus (royal pleco’s, flash pleco and the clown pleco’s), substrate dwelling Loricariinae (Pseudohemiodon, Planiloricaria etc.), Baryancistrus (gold nugget pleco, mango/magnum pleco, snowball pleco), mollusc specialists (Scobinancistrus, goldie/sunshine pleco, vampire pleco, galaxy pleco, Leporacanthicus), Chaetostoma (Rubbernoses and one of the bulldog plecos) and finally algivores/detritivores. Maybe some more will be created in the future.

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:

CourgetteReasonable in nutrition, is willingly eaten by many fishes but they might select either the flesh or skin over the other.
CucumberWhile 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 PotatoesThese 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 beansThe 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 peppersI 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 squashesI 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.

Splitting up Corydoras: Understanding the Corydoradinae Revision

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Corydoras has been revised splitting up the genus and resurrecting previously synonymized genera. But what does this all mean?

Corydoras semiaquilus, obtained from INaturalist, photo owner: Blair Chen – some rights reserved (CC BY-NC-SA)

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.

The Diet of Corydoras, lessons in carnivory

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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 sp. image from: Olivia’s and Dad’s Fishroom. https://www.facebook.com/profile.php?id=100063396450007

The Wild Corydoras Diet

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.

I believe Hoplisoma duplicareus, image from Olivia’s and Dad’s Fishroom. https://www.facebook.com/profile.php?id=100063396450007

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.

Hoplisoma sp. I assume H. atropersonatus from Olivia’s and Dad’s Fishroom. https://www.facebook.com/profile.php?id=100063396450007

What about frozen foods?

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.

Water hardness and pH, what is it and does it really matter?

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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.

Premixed foods for plecos (Loricariids) and other rasping fishes.

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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.

  1. Catering for Algivores/detritivores.
  2. Catering for Carnivores.
  3. Other niches and specialization.
  4. Will they eat it?
  5. Premade diets and their ingredients
  6. The hidden issue with premade diets
  7. Products sold for plecos

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.

Catering for Algivores/detritivores.

I have written quite a bit about this niche and therefore I recommend reading this article here which covers details into algivory, detritivory and wood eating.

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).

There is a little diversity of carnivory within Loricariidae but we don’t entirely know to what extent. I have written this article for mollusc specialists and although diverse in diets this for dwell in and around the substrate.

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

CompanyRepashy
ProductSoilent GreenSuper GreenBottom scratcherMorning wood
Dietary NicheAlgivoryAlgivoryCarnivoryXylovory
SummaryFishes 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.
Composition (%):
Protein40354520
Fat88103
Fibre881250
Moisture8888
Ash1291115
Ingredients
Spirulina Algae, Algae Meal (Chlorella), Krill Meal, Pea Protein Isolate, Squid Meal, Rice Protein Concentrate, Fish Meal, Alfalfa Leaf Meal, Dried Brewer’s Yeast, Coconut Meal, Stabilized Rice Bran, Flax Seed Meal, Schizochytrium Algae, Dried Seaweed Meal,  Lecithin, Dried Kelp, Locust Bean Gum, Potassium Citrate, Taurine, Stinging Nettle, Garlic, RoseHips, Hibiscus Flower, Calendula Flower, Marigold Flower, Paprika, Turmeric, Salt, Calcium Propionate and Potassium Sorbate (as preservatives), Magnesium Amino Acid Chelate, Zinc Methionine Hydroxy Analogue Chelate, Manganese Methionine Hydroxy Analogue Chelate, Copper Methionine Hydroxy Analogue Chelate, Selenium Yeast. Vitamins: (Vitamin A Supplement, Vitamin D Supplement, Choline Chloride, Calcium L-Ascorbyl-2-Monophosphate, Vitamin E Supplement, Niacin, Beta Carotene, Pantothenic Acid, Riboflavin, Pyridoxine Hydrochloride, Thiamine Mononitrate, Folic Acid, Biotin, Vitamin B-12 Supplement, Menadione Sodium Bisulfite Complex).Spirulina Algae, Algae Meal (Chlorella),  Pea Protein Isolate, Rice Protein Concentrate, Alfalfa Leaf Powder, Stabalized Rice Bran, Dandelion Powder, Dried Brewer’s Yeast, Coconut Meal, Ground Flaxseed, Schizochytrium Algae, Dried Seaweed Meal, Dried Kelp, Locust Bean Gum, Lecithin,  Potassium Citrate, Taurine, Stinging Nettle, Garlic, RoseHips, Hibiscus Flower, Calendula Flower, Marigold Flower, Paprika, Turmeric, Calcium Propionate and Potassium Sorbate (as preservatives), Magnesium Amino Acid Chelate, Zinc Methionine Hydroxy Analogue Chelate, Manganese Methionine Hydroxy Analogue Chelate, Copper Methionine Hydroxy Analogue Chelate, Selenium Yeast. Vitamins: (Vitamin A Supplement, Vitamin D Supplement, Choline Chloride, Calcium L-Ascorbyl-2- Monophosphate, Vitamin E Supplement, Niacin, Beta Carotene, Pantothenic Acid, Riboflavin, Pyridoxine Hydrochloride, Thiamine Mononitrate, Folic Acid, Biotin, Vitamin B-12 Supplement, Menadione Sodium Bisulfite Complex).Krill Meal, Insect Meal, Mussel Meal,  Squid Meal, Dried Brewer’s Yeast, Dried Seaweed Meal,  Lecithin,  Dried Kelp, Locust Bean Gum, Potassium Citrate, Taurine, Watermelon, RoseHips, Hibiscus Flower, Calendula Flower, Marigold Flower, Paprika, Turmeric, Stinging Nettle, Garlic, Salt, Calcium Propionate and Potassium Sorbate (as preservatives), Magnesium Amino Acid Chelate, Zinc Methionine Hydroxy Analogue Chelate, Manganese Methionine Hydroxy Analogue Chelate, Copper Methionine Hydroxy Analogue Chelate, Selenium Yeast. Vitamins: (Vitamin A Supplement, Vitamin D3 Supplement, Choline Chloride, Calcium L-Ascorbyl-2-Monophosphate, Vitamin E Supplement, Niacin, Beta Carotene, Pantothenic Acid, Riboflavin, Pyridoxine Hydrochloride, Thiamine Mononitrate, Folic Acid, Biotin, Vitamin B-12 Supplement, Menadione Sodium Bisulfite Complex).Cellulose Powder, Dried Seaweed Meal, Alfalfa Leaf Meal, Spirulina Algae, Rice Protein Concentrate, Pea Protein Isolate, Stabilized Rice Bran, Dried Brewer’s Yeast, Dried Kelp, Stinging Nettle, Locust Bean Gum, Calcium Carbonate, Potassium Citrate, Malic Acid, Taurine, Garlic,  Watermelon, RoseHips, Hibiscus Flower, Calendula Flower, Marigold Flower, Paprika, Turmeric, Salt, Calcium Propionate and Potassium Sorbate (as preservatives), Magnesium Amino Acid Chelate, Zinc Methionine Hydroxy Analogue Chelate, Manganese Methionine Hydroxy Analogue Chelate, Copper Methionine Hydroxy Analogue Chelate, Selenium Yeast. Vitamins: (Vitamin A Supplement, Vitamin D Supplement, Choline Chloride, Calcium L-Ascorbyl-2-Monophosphate, Vitamin E Supplement, Niacin, Beta Carotene, Pantothenic Acid, Riboflavin, Pyridoxine Hydrochloride, Thiamine Mononitrate, Folic Acid, Biotin, Vitamin B-12 Supplement, Menadione Sodium Bisulfite Complex).
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.

CompanyFluvalAquaCare
ProductBug Bites Pleco SticksBug Bites Pleco CrispsSpirulina Sinking WafersOak
Dietary NicheCarnivoreOmnivore/cerealsOmnivoreOmnivore/cereals
SummaryA 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.
Composition (%):
Protein3243.543.738.3
Fat1245.73.7
Fibre6333.2
Moisture??7.19
Ash9510.513.4
Ingredients
Black soldier fly larvae (30%), salmon (22%), wheat, peas, potato, dicalcium phosphate, alfalfa nutrient concentrate, calcium carbonate, calendula, rosemary.Insect Meal (Mealworm Meal 15%, Black Soldier Fly Larvae 10%), Wheat flour, Wheat Gluten, Wheat germ, Alfalfa, Spirulina, Fish Protein Hydrolyzed, Kelp (5%), Shrimp Protein Hydrolyzed, Spinach (5%), Activated Charcoal.Fish meal, Wheat, Wheat Gluten, Mycoprotein, Shrimp, Spirulina, Alfa-Alfa, Salmon Oil, Wheat germ, Spinach, Vitamins, MineralsWheat, Herring Meal, Wheatgerm, Spirulina, Alfalfa, Kelp, Oak Bark, Zeolite, Minerals, Vitamins
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.
CompanyHikariDr BasslerVitalis
ProductAlgae WafersGreen RegularPleco Pellets
Dietary NicheOmnivoreOmnivoreOmnivoreOmnivore
SummaryNot 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.
Composition (%):
Protein33575439.4
Fat418167
Fibre3241.5
Moisture10?625
Ash17101017.3
Ingredients
Fish meal, wheat flour, wheat germ meal, cassava starch, dried bakery product, dried seaweed meal, alfalfa nutrient concentrate dehydrated, dehydrated alfalfa meal, brewers dried yeast, soybean meal, fish oil, krill meal, spirulina, garlic.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.
CompanyOaseTetraNew Life SpectrumFish Science
ProductOrganix Veggievore TabsSpirulina WafersAlgae MaxAlgae wafers
Dietary NicheCarnivoreHerbivoreAlgivoreOmnivore
SummaryA 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.
Composition (%):
Protein35283442
Fat13687.5
Fibre1582.2
Moisture?91010
Ash9??8.5
Ingredients
Whole Salmon, Whole Shrimp, Wheat Flour, Kelp, Whole Herring, Wheat Germ, Vitamins and Minerals.Cereals, Vegetable protein extracts, Derivatives of vegetable origin, Yeasts, Oils and fats, Algae (Ascophyllum Nodosum 3,0%, Spirulina 0,9 %), Minerals.
Vitamins: Vitamin D3 1810 IU/kg. Trace elements: Manganese (manganese (II) sulphate, monohydrate) 81 mg/kg, Zinc (zinc sulphate, monohydrate) 48 mg/kg, Iron (iron(II) sulphate, monohydrate) 32 mg/kg. Colourants, Preservatives, Antioxidants.		Seaweed (Ulva latuca, Undaria pinnatafida, Eucheuma cottonii, Eucheuma spinosum, Chondrus crispus, Porphyra umbilicus), Krill (Euphasia superba), Squid (Dosidicus gigas), Whole Wheat Flour, Kelp, Spirulina, Fish (Brevoortia tyrannus), Fish Oil, Garlic, Ginger, Astaxanthin, Marigold, Bentonite Clay, Sea Salt, Vitamin A Acetate,Vitamin D Supplement,Vitamin E Supplement, Vitamin B12 Supplement,Niacin, Folic Acid, Biotin, Thiamine Hydrochloride, Riboflavin Supplement, Pyridoxine Hydrochloride, Calcium Pantothenate, L-Ascorbyl-2-Polyphosphate (Vitamin C), Choline, Chloride, Ethylenediamine Dihydroiodide, Cobalt Sulfate, Ferrous Sulfate, Manganese Sulfate, Tocopherols (a preservative).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.

South America’s Electric Fishes: Gymnotiformes. A Guide for the Aquarist.

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Steatogenys cf. duidae

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.

Fricke, R., Eschmeyer, W. N. & Van der Laan, R. 2024.  ESCHMEYER’S CATALOG OF FISHES: GENERA, SPECIES, REFERENCES. (http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp). 

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.