How Many Cory Catfish in a 5 Gallon Tank?

Last Updated on August 8, 2022 by cmoarz

Corydoras are great starter fish for someone whos relatively new to the hobby. While they are slightly more sensitive to water quality than some of the other fish on this list, they are still very hardy overall. So, if you’re just starting out, how many cory catfish can you put in a 5-gallon tank?

The answer is none! You can’t put corydoras in a 5-gallon tank, here’s why.

Corydoras are shoaling fish

What is a shoaling fish? A shoaling fish is a fish that lives in groups. In the wild, corydoras live in large groups of up to several hundred fish. This is because they are very social creatures that need the company of their own kind to feel comfortable and secure.

A shoaling fish is sort of like a school of fish, they like to be in groups. The difference is; shoaling is more like a loose social group of friends while schooling fish all move and behave as one.

You can’t just have 1 or 2 cories, you need 5 to 6 corydoras to make a shoal. A 5-gallon tank can not even accommodate 1 adult corydoras, let alone 5 or 6 of them.

When corydoras aren’t kept in small groups of 5 minimum, they become stressed, and lonely and may even stop eating. So, for the sake of your fish, don’t put them in a 5-gallon tank!

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Corydoras have a fairly large bioload

5 gallons of water isn’t very much water and can become polluted very quickly. This is especially true when you add fish that produce a lot of waste like corydoras.

Corydoras are bottom feeders and eat a lot, as such bottom feeders tend to have a much larger bioload than other types of fish. This means they produce a lot more waste than other fish, which can quickly pollute a small tank like a 5-gallon.

A filter might be able to keep up with a 5 gallon with a betta or something similar in it, But there is no way a filter could keep up with the bioload of a group of 5 corydoras. The water would become so polluted that the fish would likely die or the maintenance would be water changes almost every day.

A 5-gallon also doesn’t offer enough area for bacteria to grow to properly cycle the tank for such a bioload. This is another big reason why a 5-gallon can’t support corydoras.

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Corydoras need much more swimming space than a 5 gallon can offer

As said above, corydoras love to shoal, which means they all kind of move together. They love to swim around and explore their tank, and they need enough room to do so.

Corydoras are not big fish, but they still need a good amount of space to swim around and be comfortable. A 5-gallon is just way too small for them and they will quickly become stressed in such a confined space.

They will eventually become immobile, lethargic, and stop swimming altogether if they don’t have enough room to move around.

This is not a good sign and means they are very stressed, which will make them more susceptible to disease.

The bottom line is that corydoras need a lot more space than a 5-gallon can offer.

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The minimum tank size for corydoras is 20 gallons

With all that said, For 6 corydoras you should only consider getting a 20-gallon or larger tank. This is the minimum size tank you should get for corydoras, and even then it’s still a bit of a tight fit.

Ideally, you would want a 30-gallon or larger tank for 6 corydoras, but a 20-gallon will do in a pinch. Just know that they will be much happier and healthier in a larger tank.

Corydoras are great fish, but they just don’t do well in small tanks like 5 gallons. So, if you want to keep corydoras the minimum tank size you should get is 20 gallons. Trust me, your fish will thank you for it!

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Bottom line

If you truly love your fish and only want to provide the best care for them then you will not put them in a 5-gallon tank. A 20-gallon tank is a bare minimum you should even consider for corydoras.

The number of corydoras in a tank should never be less than 5-6. They are social fish who feel more at ease and secure when they are in groups.

If you follow these guidelines, Your fish will live long and happy lives and you will find much entertainment and joy in watching them swim and play in their tank!


Owner of and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!