How Many Cory Catfish in a 30 Gallon Tank Can You Have?

Last Updated on August 9, 2022 by cmoarz

Corydoras need a fairly large tank, and a 30 gallon is a good start in giving them what they require. With that said, you may need to know how many cory catfish you can put in a 30-gallon tank before it’s overstocked. There are a few things you need to consider.

There are 2 maximum limits for corydoras in a 30-gallon and it depends on your filtration

The amount of cory catfish in a 30-gallon tank safely will depend entirely on the type of filtration system you use. If you have a smaller, hang-on back filter, sponge finger of appropriate size, canister filter, or any other type of self-contained loop filter, You are going to be limited to a maximum of 12 corydoras per 30 gallons.

Corydoras produce quite a bit of waste, and even though there is a good chunk of water volume in a standard 36″x13″x16″ 30-gallon tank, with these simple closed loop filters, water quality is expected to drop rapidly after 12 corydoras.

This would mean more water changes, which is not really an issue, but you do need to be aware that your filtration system will need to be on the higher end of things to accommodate the bioload of more than 12 cory catfish.

With that said, If you’ve got an overflow tank with a constant supply of fresh water being pumped in and good surface skimming, you could theoretically house upwards of 24 corydoras in a 30-gallon tank, perhaps more.

The rule of thumb is 1″ per gallon of water for cory catfish, but that’s really more of a minimum as they do better in groups.

So, if you’ve got a 30-gallon tank, you could house anywhere from 12 to 24 corydoras, depending on your filtration system. Just keep in mind that the more corydoras you have, the more filtration you’ll need.

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Never put less than 6 corydoras in a single tank

Corydoras are shoaling fish, which means they like to live in groups. In the wild, they can often be found in shoals of 100 or more fish. While you’re not going to be able to recreate that in your home aquarium, you should try to have at least 6 corydoras in a single tank.

Anything less than that and your corydoras will likely be stressed, which can lead to health problems.

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Adding more fish to a 30-gallon with 12 corydoras

Since corydoras mostly occupy the bottom of the tank, you’ve got a lot of room to add more fish. If your filtration system can handle it, you could easily add several more species of mid and top-water column fish.

You could also add other bottom-dwelling fish like loaches, plecos, or even some tetras. Just be sure not to overstock the tank and keep an eye on water quality.

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Making the most of your 30-gallon for your corydoras

30 gallons only provides so much room for swimming around in a shoal. Corydoras will also require plants and objects to pick around in and call home.

So to alleviate some of the lack of space for swimming, add more objects. The more objects in a tank, the happier your cories will be just picking around rather than just swimming in a line.

The added bonus to adding plants and objects is that it provides your corydoras with more places to hide when they need it. Stress can cause health problems in corydoras, and a good hiding spot can help reduce that stress.

Plants can also help reduce the bioload and give you more options for additional fish.

So when stocking a 30-gallon tank with corydoras, remember to consider not just the fish but also the plants and objects you’ll need to provide them with a happy and healthy home.


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!