Corydoras Care: Group Size, Sand or Gravel, and Water for Three Common Species

One genus, many ranges

Aquarium Co-Op says the genus holds more than 160 species, running 1 to 3 inches in the hobby, with sharp spines in the fins that can produce a mild venom when the fish is stressed. It adds that you shouldn’t catch them with bare hands 1. Seriously Fish now lists the bronze, pepper and pygmy corys under the genera Osteogaster, Hoplisoma and Gastrodermus, and says each was long known as Corydoras. Co-Op and FishBase still use Corydoras, so we do too.

We checked three common species against FishBase.

The pepper cory is the outlier. FishBase puts it at 18 to 23 °C (64 to 73 °F) and Seriously Fish at 22 to 26 °C (72 to 79 °F). Only the very top of the first range meets the bottom of the second. Seriously Fish also says the pepper cory needs steady temperature and pH 3. Aquarium Co-Op says peppered and julii corys sit on the cooler end of its 72 to 82 °F range for most species, while sterbai can take more heat, and it gives pH 6.5 to 7.8 1. Our reading: for the bronze and pygmy corys the two sources overlap across most of 72 to 79 °F. For the pepper cory the overlap is only 72 to 73 °F. FishBase classes it as subtropical and lists Argentina, Brazil and Uruguay as its range, which may explain the cooler figure. We found nothing that tests either range in aquariums, so pepper corys are the ones to keep a close eye on.

Our heater guide and pH guide cover how to hold those numbers.

Group and tank size

Co-Op says to keep six or more of the same species, since they want safety in numbers. It suggests 10 gallons for dwarf species and 20 or more for the rest 1. FishBase says groups of five or more and a minimum aquarium of 60 cm (about 24 inches) for the bronze and pepper cory 5 6. Seriously Fish gives a tank about 31 x 12 inches (about 19 gallons) for bronze corys, 24 x 15 inches (about 18 gallons) for pepper, and 18 x 12 inches (about 11 gallons) for a large group of pygmies 2 3 4. Those agree on the 18 to 20 gallon floor for the larger species. Our stocking guide shows how that fits with other fish.

Mixing species in one group is not what the sources advise. Co-Op says “all of the same species” 1.

Substrate

Seriously Fish says bronze corys are best on fine sand, with rounded gravel acceptable if it’s kept scrupulously clean 2. For the pepper cory it says they prefer sand because they enjoy rooting for food, and can get barbel infections in poorly maintained gravel 3. Co-Op prefers smooth sand or gravel, since they use their barbels to find food. It adds that the CEO found sharp substrate in the wild, so eroded barbels may come from poor water quality rather than the gravel 1.

Food

Seriously Fish says corys are foraging omnivores that take most sinking dried foods and small live and frozen food, and that they shouldn’t be expected to survive on leftovers or to clean the tank 2. Co-Op says larger foods such as worms and gel food sit on top of the substrate where corys can reach them, and that in a tank with aggressive eaters they can be outcompeted and waste away 1. They aren’t primarily algae eaters 1.

Tank mates

Co-Op says corys fit with almost any community fish that won’t eat or attack them, and names goldfish as a bad match because they inhale anything that fits in their mouth 1. Seriously Fish rates all three species as peaceful 2 3 4. They pair well with the small fish in our neon tetra and guppy guides. Our angelfish guide lists corys among the fish Aquarium Co-Op has paired with angelfish.

FAQ

How many corydoras should I keep? Co-Op says six or more of one species 1. FishBase says five or more 5.

Do corydoras need sand? Seriously Fish prefers sand, or clean rounded gravel for the bronze cory 2 3.

What temperature should I use? Most overlap between 72 and 79 °F, except the pepper cory, where FishBase and Seriously Fish disagree 3 6.

Will corydoras clean my tank? Seriously Fish says no 2.

Can corys live with goldfish? Co-Op says no 1.

Can I use aquarium salt with corydoras? We found no study on it. Our aquarium salt dose chart shows what the sources say about catfish and salt.