Corydoras & Bottom-Dwelling Catfish: More Than a Cleanup Crew

The Cleanup-Crew Myth

Corydoras do forage along the bottom and eat food that settles there, which is how they got their reputation. But calling them a cleanup crew flattens a fish with its own diet, social and habitat needs into a piece of equipment, and no fish replaces water changes and gravel cleaning.

They Need Their Own Food

What drifts down from a surface feed rarely adds up to a full diet. Give corydoras a sinking wafer or pellet of their own, ideally in the evening when they are most active, alongside whatever you feed the rest of the tank. Frozen foods add variety. Corydoras left to live on scraps end up thin.

A Real Group

Corydoras are shoaling fish. OATA advises keeping them in groups of at least five, and warns that fish kept singly or in too-small groups often become stressed. A proper group forages openly and rests in loose clusters; a lone cory tends to hide.

OATA suggests a tank of at least 80 liters (about 21 gallons) for a shoal of the smaller catfish species, with a heater, a filter and cover from plants, wood or caves.

Soft Ground for Barbels

Corydoras find food with their barbels, the whisker-like feelers they drag through the substrate all day. OATA recommends sand or fine gravel because all catfish have sensitive barbels that can be injured. Sand also lets them sift the way they would in the wild.

Take care when netting or handling them: most catfish have spines on their front fins that can snag in a net or prick a finger.

Not Every Catfish Is a Cory

Corydoras are among the gentlest, most beginner-friendly catfish. The same store section may sell species that grow far bigger, become territorial, or need different water: OATA notes catfish range from tiny Otocinclus at about 1.5 inches (4 cm) to red-tailed catfish that can reach about 3 feet (1 meter). Always check a species' adult size before buying "a catfish".