Cory Catfish have become very popular in the aquarium hobby. Their lively character and relatively easy care make them the ideal catfish to keep in many community tanks.

Unfortunately, a lot of misinformation is out there. Especially regarding pet stores, that make wrong recommendations on how many Cory Catfish to keep. In this blog post, we’ll be discussing how many Cory Catfish should be kept together so that they can live a long and healthy life.

Do corydoras need to be kept together?

Cory catfish are great beginner fish, and many pet stores try to sell these fish to the starting aquarist. Unfortunately, they often don’t mention they need to be in group.

Cory Catfish always need to be kept together, and will not feel happy alone. In the wild, Cory Catfish live together in groups of hundreds of fish, seeking protection from predators. In an aquarium, this should be no different.

Unlike popular belief, Cory Catfish are not great schooling fish in your aquarium. They will not always be in each other’s presence. This is why you can perfectly see them hanging out alone or with 2/3. However, this doesn’t mean that Cory Catfish don’t need the presence of each other and always need the possibility to group with their peers. 

How many Corydoras should be kept together?

Cory Catfish are group animals, which means they need to be kept in groups in order to be happy and healthy. But how many Cory Catfish should I keep?

At least 6 Cory Catfish of the same species should be kept together. Cory Catfish will feel the best in groups of 10 or more if your tank is suited. How many Cory Catfish you can keep together depends on the tank size, tank mates, and filtration. 

Pet stores often wrongly claim that you can perfectly keep 2 Cory Catfish together. Pet stores only say this so they can sell more fish or don’t know, and not because they are concerned with the health of the fish they are selling.

In a 5 gallon tank

In a 5 gallon tank, no Cory Catfish should be housed. Since a group of at least 6 is necessary for them to feel good, a five-gallon is too small to house a small group. Even small species like Pygmy Cory Catfish will feel uncomfortable.

In a 5 gallon tank,  many fish will not be happy. Especially Cory Catfish, who might not seem to move a lot, need enough space to dig and search for food. Cory Catfish are often sold as juveniles in pet stores. They might seem very small but usually grow up to be around 2-3 inches.

You might think that smaller dwarf corydoras (C. hastatus, C. pygmaeus) can be suitable. However, these species are even more active than bigger species and will usually hang out in the middle layer of the tank, swimming a lot.

If you are searching for some nano species to live in a 5 gallon tank, think about shrimp, a (wild) betta fish, or pearl danios.

As you can see, pygmy Corydoras can swim in the middle layer of the tank too. Photo by mobile_gnome

In a 10 gallon tank

10 gallons is around the minimum size for keeping Cory Catfish. Still, there is some controversy about whether this is suitable for Cory Catfish. 

In a 10 gallon tank, 6 to 8 small Cory Catfish can be kept, depending on filtration and tankmates. Most species will prefer a bigger tank, so only a group of dwarf species can be housed. 

Species

Depending on the species, more or less Cory Catfish can be kept together. It’s obvious that the bigger the species, the bigger it’s requirements will be in terms of tank size. 

A 10-gallon tank is only suited for small Cory Catfish species like dwarf Corydoras. These are Corydoras pygmeaus and Corydoras hastatus. Maybe also a small species like C. julii/ C. trilineatus. It’s certainly not suited for bigger species like the Bronze Cory Catfish or Sterbai Corydoras.

If you want to know more about small cory catfish species that can live in a 10 gallon tank, make sure to visit our small cory catfish list. It covers 5 species that are perfect to keep in a 10 gallon tank. Dwarf cory catfish types.

In a 15 gallon tank

Keeping Cory Catfish in a 15 gallon tank is similar to keeping them in a 10 gallon tank: many species will need a 20 gallon or more to live happily.

Around 6 to 8 Cory Catfish of small species like dwarf Cory Cafish can be kept in a 15 gallon, depending on tank mates, filtration . Bigger species like Bronze Cory Catfish can’t be kept in this tank size.

Corydoras melanistius. As you can see, they get quite big. Photo by Britzke

In a 20 gallon tank

In a 20 gallon, there are more options, both in terms of group size and in terms of species. You can keep most species in this tank and it’s a popular size for many breeders to breed Cory Catfish in.

In a 20 gallon tank, between 8 and 10 Cory Catfish can be housed. Depending on the species and tank mates. Bigger groups of 10-14 fish are possible with small species like dwarf Cory Catfish.

There are sold two common types of 20 gallon tanks: the 20 gallon long and the more common 20 gallon high tank. As the name implies, the 20 gallon long is less high and thus has more bottom surface. Whereas a 20 gallon high may be better for some community tanks, Cory Catfish love scattering through the bottom. 

As a result, it’s also possible to keep some more Cory Catfish in a 20 gallon long tank. Of course, you will still need to pay attention to the other species in the tank

In a 29/30 gallon tank

In a 20 gallon, there are more options, both in terms of group size and in terms of species. You can keep most species in this tank and it’s a popular size for many breeders to breed Cory Catfish in.

In a 20 gallon tank, between 8 and 15 Cory Catfish can be housed. Depending on the species and tank mates. Bigger groups of 15-20 fish are possible with small species like dwarf Cory Catfish.

A 29 gallon tank with Pygmy Cory Catfish. Photo by mobile_gnome

Mixing corydoras species

There are so many Cory Catfish species, that it might be tempting to start and mix species. 

It’s not recommended to mix Cory Catfish species in small groups. The Cory Catfish will group together, but always prefer their own species to hang out with. Cory Catfish might also crossbreed, which creates unwanted hybrids.

When talking about how many Cory Catfish should be kept together, this means one species: only one species should be kept together. Only if you have a big tank like a 50 gallon, multiple groups can be kept together. This way, Cory Catfish can always group with their own species. 

Conclusion

Cory Catfish always need to be kept together, no matter what the pet stores say. The minimum tank size for dwarf Cory Catfish is 10 gallons, although a 20-gallon tank is far better.

The minimum group size of Cory Catfish is 6 specimens, but the more the better. The bigger the tank, the more Cory Catfish can be housed in it.

It’s not recommended to mix cory Catfish species. This fish will always prefer their own species. Cross breeding may even occur, resulting in not-wanted hybrids.