Corydoras Catfish

Corydoras catfish are the workhorses of the community aquarium — peaceful, armored, endlessly busy bottom-dwellers that scour the substrate for scraps while remaining completely non-aggressive toward tankmates. With over 160 recognized species ranging from the tiny pygmy cory to the larger emerald cory, the genus Corydoras offers an option for virtually every aquarium size and aesthetic.

Taxonomy & Popular Species

The genus Corydoras belongs to the family Callichthyidae (armored catfish). Popular aquarium species include:

• Bronze Cory (C. aeneus) — the most widely kept; copper-bronze metallic sheen; highly adaptable
• Peppered Cory (C. paleatus) — marbled grey-green pattern; cool-water tolerant
• Emerald Cory (C. splendens) — larger; vivid green metallic sheen; very active
• Sterbai Cory (C. sterbai) — distinctive spotted pattern with orange pectoral fins; tolerates higher temperatures; ideal for discus tanks
• Panda Cory (C. panda) — white body with black patches; a popular nano/planted tank species
• Pygmy Cory (C. pygmaeus) — under 1 inch; truly nano-sized; active schooling mid-water dweller unusual for the genus

Natural Habitat

Wild corydoras inhabit shallow, sandy-bottomed streams, river margins, and seasonally flooded areas across South America. Most species prefer soft, warm, slightly acidic to neutral water with a fine sand substrate that they can dig through without damaging their delicate barbels. They school in large numbers, foraging along the bottom for organic debris, invertebrates, and plant material.

Tank & Substrate Requirements

The single most important consideration for corydoras is substrate: use fine sand or smooth, rounded gravel. Sharp-edged gravel erodes the corys' delicate barbels (the sensory whiskers around their mouths), leading to infection and shortened lifespan. 10 gallons suits a small group of 6 pygmy corys; larger species like bronze or sterbai corys need 20+ gallons for a proper school. Corydoras should always be kept in groups of 6 or more — isolated individuals are stressed and prone to disease.

Diet

Bottom-feeding omnivores. In captivity: sinking catfish pellets and sinking wafers as the staple; supplement with frozen bloodworms, tubifex, and daphnia. They will scavenge uneaten food from the substrate, but should not be relied upon to "clean" the tank — dedicated feeding ensures they receive adequate nutrition. Feed at lights-out when they are most active.

Breeding

Corydoras are among the more accessible catfish to breed in captivity. They scatter eggs on glass surfaces, plant leaves, and substrate. Spawning is often triggered by a partial water change with slightly cooler water (simulating a rainy season). Eggs hatch in 3–5 days. Remove eggs to a separate hatching container to prevent adult predation. Fry are initially fed infusoria and micro worms before graduating to baby brine shrimp.

Common Health Issues

• Barbel erosion — most common problem; caused by sharp substrate or poor water quality; improve substrate and clean water; barbels can regenerate if damage is not severe
• Red blotch disease — red patches on body; bacterial; improve water quality and treat with antibiotics if severe
• Ich — white spots; treat with medication at half dose if using salt (corys are scaleless and more sensitive than scaled fish)
• Catfish parasites — gill flukes and skin flukes; treat with praziquantel