The Corydoras genus includes more than 142 species, all of which live in South America. Together with a number of other genera, they form the family Callachtidae or Armored Catfish.
They got their name Armored Catfish because they lack scales. Instead of scales, they have bony plates under a mucous membrane that act like a kind of armor. Together with the spiky anterior dorsal ray and pectoral fin rays, they make a tricky bite for predators.
All Corydoras species can also survive in deoxygenated water. They then shoot to the surface and take a gulp of air that is forced through the intestines. The intestines then absorb oxygen from the water.
Sexing Corydoras is sometimes a bit difficult. Usually the female is a bit bigger and plumper than the male. Also the dorsal fin is often slightly different in shape. The dorsal fin is somewhat pointed in the male and somewhat rounded in the female.