While bare bottom aquariums are very popular they do not provide the stimulation to many fishes that can be provided by providing a substrate. It is ones own opinion slightly and worth researching further.

The two main substrates you might see:

• Gravel: It is okay if not housing digging fishes or those that pick up gravel with their mouth but that does limit stocking choices. Generally aiming for those gravels with softer edges does help as well. It traps waste very easily due to the many holes and prevents any digging behaviour of fishes. Sharper gravels can damage many fishes mouth anatomy or preventing hiding behaviour in other fishes.
• Sand: This and fine gravels allows for many fishes to dig, hide and interact with the substrate. many fishes are simply evolved for this substrate. Waste sits on the top and as long as it is disturbed frequently, some snails can help with this it wont have any anaerobic issues, although a finer level helps a lot with this. Definitely the substrate I recommend.
• A quick warning, unless for harder water fishes avoid coral sand as it will raise many of these parameters and is not suitable for many different fishes as a result.

There are other variations on this, mixing sand and gravel could be an idea worth trying and wont have the issues with gravel unless the fish is picking up the gravel with their mouth. Pebbles too large to be picked up by fishes can have an enrichment purpose but also allow you to let plants root before adding fishes that might dig.

Botanicals are great but maybe not for the beginner, I will discuss later on, on this website.

How much substrate do I use?

Generally to avoid a build up of anaerobic bacteria and the compounds/toxins that involves it is best to only have a few centimetres.

Now the more honestly my opinion stuff as it can’t help not get mentioned here. It is political but this website is about fishkeeping not horticulture and plants. The focus is the fish where plants might be an addition not the reverse where plants are the focus.

What about plant substrates?

I would discuss this but it adds in a lot of complexities. All will release ammonia and for some generally a lot at first. I casually deal with horticulture and therefore there are such a range of variables that make it much more difficult to predict. Aquarium substrates generally are better then any not aimed at the aquarium.

A lot of planted tanks are more aimed either short term or for plant growth rather then fish welfare and care. A bit of a controversial idea but I can discuss further if required.

So do plants need plant substrates?

It depends on the plants, plants need nutrients but this can be provided for in a variety of manners. I wont lie and say I’ve had many successful long term planted tanks without planted substrates, just sand.