How Many Cory Catfish In A 20-Gallon Tank?

Cory catfish have hundreds of species ranging from one to four inches. The smaller cory’s between one and two inched can be grouped into shoals of ten to twelve, while the bigger cory’s between two to four inches can be grouped up to eight per 20-gallon tank. 

Cory catfish are social animals that enjoy the company of their own species. Better known for their peaceful and timid natures, they can add a spark of playfulness to a tank as they school together. But, of course, how many cory catfish you put together depends on the size of your tank so as not to overtax the bio-load capacity of your tank.

How Many Cory Catfish In A 20-Gallon Tank?

Cory catfish are social animals that do well in the company of other community fish. They prefer the company of their own species, forming a school that can add playfulness to your tank and makes it more visually attractive and exciting.

A 20-gallon tank is a comfortable enough size to keep six normal-sized cory catfish together.

Smaller cory catfish, like the pygmy catfish, reach just over an inch in length, allowing a 20-gallon tank to house shoals of eight to ten comfortably if you add them to a tank of other community fish.

A rule of thumb when calculating how many fish to keep in a tank is that you need one gallon of water for every inch of fish. But it is more accurately measured when using the volume of the fish when you have wider fish.

Corydoras Catfish

How Many Cory Catfish Should You Keep Together?

Cory catfish find safety in numbers. Therefore, a minimum number of six same species of cory catfish is highly recommended. With a larger number of these interesting fish together, you will start to see more playfulness in your tank as the fish thrive and feel safer in larger groups.

Can Cory Catfish Live Alone In A 20 Gallon Tank?

Cory catfish are gentle, social, and friendly fish that find safety in numbers of their own kind.

Although it’s best to keep at the very least two or three same species of catfish together, it is possible to keep one on its own. Still, they will be even more timid than usual. They will not thrive as well as they would in a larger group, with a possibility of a shortened lifespan.

What Shape Tank Is Best For Cory Catfish?

Cory catfish are quick swimmers that keep together in schools darting around the tank at the mere hint of danger.

As bottom dwellers, they scavenge and sift through soft substrates and enjoy ornaments where they can hide. Live plants, either buried or floating, are also an excellent addition for these timid fish to provide cover and a place to hide and rest.

Cory catfish do better in longer tanks as they do not need much depth. They only dart to the surface to eat floating food or gulp in a bubble of air before returning to the lower level of the tank, where they feel safest.

So long rectangular tanks work best to give them the freedom to move. Avoid deep tanks with narrow bases, such as round tanks; they don’t provide the space required to provide a happy environment for catfish to scavenge and play.

Can You Mix Different Cory Catfish Species In A Tank?

Cory catfish are non-aggressive and non-territorial creatures, so mixing different species of cory catfish is possible. However, cory catfish species tend to stick to their own kind, so you may find single stragglers swimming alone if you add catfish from a different species.

Cory catfish can mate outside their species, leaving you with unwanted hybrids in your tank if you have more than one species of catfish.

The recommended solution is to stick to one species. Instead, add more numbers of one kind of cory catfish to your tank.

What Tank Mates Can You Keep With Cory Catfish?

Cory catfish are bottom dwellers scavenging through soft sandy substrates for leftover foods, so it makes sense to add similar-sized community tank mates occupying different levels of the tank.

Try keeping the size of your fish similar to avoid larger fish picking on or eating your cory catfish.

Most nano aquarium tank fish go well with smaller cory catfish,

  • Swordfish
  • Platy
  • Hatchetfish
  • Livebearers
  • Danios
  • Tetras
  • Rasboras
  • Small shrimp
  • Small snails
  • Other similar-sized Corydoras
  • otocinclus
  • Fancy Guppies
  • Gouramis
  • Kuhli loaches

What Is A Recommended Tank Size For Cory Catfish?

There are hundreds of cory catfish species, each of which comes in different sizes. That said, the minimum recommended tank size to keep a small school of six cory catfish is a 20-gallon tank.

This size allows smaller cory catfish or smaller quantities of cory catfish to have enough space to move around comfortably.

The large species that grow above 2 inches and are kept in small shoals of 6 should preferably be added to a 30-gallon tank.

If you want to increase your numbers or add two types of cory catfish to your tank, to increase competition and make the tank more visually stimulating. Then consider looking at a 50-gallon tank.

Below is a quick reference table of facts about some popular cory catfish you may find at the pet shop.

Bandit Cory CatfishCorydoras melini5 years +2 inches3 to 610 gallons15 -20 gallons
Bronze Cory CatfishCorydoras aeneus5 years +2.5-3 inches3 to 615 gallons20 – 30 gallons
Julie Cory CatfishCorydoras julii5 years +2.5 inches620 gallons30 gallons
Panda Cory CatfishCorydoras panda10 years +2 inches615 gallons20 gallons
Salt And Pepper Cory CatfishCorydoras paleatus4 years2.3 inches620 gallons30 gallons
Skunk Cory CatfishCorydoras arcuatus4 years3 inches5+20 gallon30 – 50 gallons
Threestripe Cory CatfishCorydoras trilineatus10 years2.5 inches620 gallons30 gallon
Dwarf Cory CatfishCorydoras hastatus3 years1 inch4 to 610 gallons15 gallons
Pygmy Cory CatfishCorydoras pygmaeus3 years1 inch410 gallons15 gallons
Sterba’s Cory CatfishCorydoras sterbai10 years +2.5 inches6 +20 gallons30+ gallons
Adolfo’s Cory CatfishCorydoras adolfoi5 years2.2 inches620 gallons30 gallons
Emerald Cory CatfishCorydoras splendens10+ years3 inches6 +20 gallons30 -50 gallons

Looking for More Tank Sizes for Cory Catfish?

How Many Cory Catfish in a 5 Gallon Tank

How Many Cory Catfish in a 10 Gallon Tank

How Many Cory Catfish in a 15 Gallon Tank

How Many Cory Catfish in a 29 Gallon Tank


Corydoras catfish are timid and friendly creatures that inhabit the lower part of your aquarium. In a 20-gallon tank, you can add between 6 to 10 cory catfish, depending on the species. Some only reach an inch in length, while others can grow to 3 inches. The rule is that every inch of fish needs one gallon of water.