How Many Cory Catfish in a 20-Gallon Tank? Comprehensive Guide

Alison Page

Alison Page


How Many Cory Catfish in a 20 Gallon Tank

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Corydoras catfish are one of the most popular fish in the tropical aquarium hobby. These cute little fish are easy to care for and can be highly entertaining, making them a firm favorite with beginners and experienced fishkeepers alike.

Corys, as they are also known, make an excellent addition to a peaceful community tank. So, you might be wondering how many Corydoras you can keep in a 20-gallon tank.

Read this guide to find out how many Corys should live together so that your fish will enjoy a healthy, long life.

What Are Corydoras Catfish?

Corydoras catfish are also known as Cory catfish or, simply, Corys.

There are over 100 varieties of Corys in this freshwater genus, all of which are peaceful fishes that make an excellent addition to a community setup.

Corydoras are collectively referred to as “armored catfish” because of the hard, bony plates that cover the sides of the fish’s body.

Some of the species also have venomous barbs that are used as protection. So, when netting or handling your Corys, take care not to damage the barbs or touch them.


Corydoras are generally native to various countries across South America, where they live in shallow, still water bodies.

In the natural environment, Cory catfish are found in streams and small rivers where they live on the substrate, hiding amid plants and driftwood.

In Cory’s habitat, the lighting is poor, and the fish spend their time digging in the soft, sandy substrate for food.

There’s no doubt that Corydoras are schooling fish since they live in huge groups of hundreds or even thousands in their wild environment.


In captivity, Corydoras catfish usually live to around 5 years of age. However, some aquarists report some individuals have reached almost 30 years old!

I’ve had several Corys who have lived in captivity for at least 10 years.

The friendly Cory will never chase or hassle a tank mate, and they can be kept safely with shrimp, even leaving babies alone.

Temperate Water

Although Corydoras catfish are tropical fish that live in warm water with a temperature of between 74° and 80° Fahrenheit, these remarkable fish can tolerate slightly cooler conditions than many tropical species.

That ability to live in cooler water and their peaceful nature makes the Cory catfish suitable for life in coldwater community setups with goldfish, White Cloud Mountain minnows, etc.

Popular Corydoras Catfish Species

As we mentioned earlier, there are over 100 species of Corydoras catfish to choose from, ranging in size from 1.5 to 3 inches in length.

Here are a few of the most commonly seen pet Corys that are readily available in the trade:

Of course, there are much more popular Cory catfish to choose from, and they all make peaceful fish tank mates for your community setup.

Do Corydoras Need To Be Kept Together?

Unfortunately, pet stores often neglect to inform customers that these sweet little fish need to live in groups.

However, you now know that wild Corys live in massive groups, so it follows that the same applies in captivity.

That said, unlike many fish species, Corys don’t tend to swim or school together. In fact, you’ll often see your catfish spending time alone or in groups of two or three. However, these fish do need the company of others of their kind to feel safe and secure.

Ideally, you should keep no fewer than six Corydoras in your tank. However, if you have a large enough aquarium, we recommend that you keep a dozen Cory catfish or even more individuals than that.

How Many Cory Catfish In A 20-Gallon Tank?

How Many Cory Catfish in a 20 Gallon Tank

So, how many Cory catfish can you keep in a 20-gallon tank?

A 20-gallon fish tank is just about the most popular size of an aquarium with many hobbyists, and it’s also the go-to tank size for many Cory catfish breeders.

In a 20-gallon tank, you can generally keep between eight and 10 Cory catfish, depending on the species of Corydoras you choose and what tank mates you want to keep with them.

Of course, if you opt to keep smaller species, such as dwarf or Pygmy corydoras, you can keep up to 14 individuals if you want to.

Tank Shape

Since Corydoras catfish of all species are bottom-dwellers, a long, shallow tank is preferable to house these lovely little fish.

Corys spend most of their time living on the bottom of the tank, foraging around plant bases and digging around in the substrate while hunting for tidbits of leftover food.

Occasionally, you’ll see a Cory darting to the surface to snatch a gulp of air before returning to the bottom again. That’s perfectly normal behavior that enables the Cory to survive in stagnant water and is not necessarily a reflection on the water quality in your fish tank!

However, they could become stressed if the Corys can’t easily reach the water’s surface.

Stress causes the fish’s immune system to be compromised, leading to disease outbreaks and parasite attacks. So, a shallow tank is the best choice for these fascinating fish.

Tank Lid

Corydoras catfish don’t generally jump, preferring to hide amid plants or under pieces of driftwood when alarmed.

However, we recommend having a tank with a lid or cover slide in case of accidents.

A covered tank also keeps dust and foreign objects out of the water and minimizes evaporation.

Can You Mix Different Corydoras Species?

As there are so many different Cory catfish species, you might be wondering if you can keep a selection of them in your community tank.

In theory, there’s no reason why you can’t combine several different Cory species. However, you should know that the different varieties prefer hanging out with their own species. So, you might end up with a few lonely individuals left out in the cold.

In addition, since they are the same species, Cory catfish can crossbreed, potentially leaving you with unwanted hybrids in your tank.

For those reasons, we recommend that you stick to keeping a group of one cory species unless you have a very large tank that enables you to keep multiple groups of appropriate numbers.

Final Thoughts

I hope you enjoyed our guide to how many Cory catfish you can keep in a 20-gallon aquarium. If you found the information helpful, please take a moment to share the article before you go!

Corydoras catfish are fun, peaceful little fish that are super-easy to care for and incredibly hardy, making them the ideal choice for a beginner’s tank.

100 species of Cory catfish to choose from, so there are plenty of options to consider.

Corys must be kept in groups of at least six individuals, ideally in a shallow, rectangular tank with plenty of planting and driftwood for hiding places.

Corys can also tolerate cooler water conditions, making them perfect candidates for life in a Fancy goldfish community tank.

Do you have Cory catfish in your aquarium? Why not tell us what varieties of Corys you keep in the comments box below?

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