Sifters of the riverbed
A corydoras feeds face-down, working along the bottom in a loose, cheerful group, taking mouthfuls of substrate and sifting out insect larvae, small worms and tiny crustaceans before blowing the sand back out through its gills. The barbels around its mouth — the whiskers that give catfish their name — are tasting organs, constantly sampling the floor for food. In the wild that floor is soft sand or fine silt over huge areas. Everything about feeding this fish at home copies that picture: food delivered to the bottom, in small pieces, across enough area that a whole school can sift side by side.
The clean-up crew myth
Corydoras suffer from one of the aquarium hobby's most persistent misunderstandings: that they live on whatever the other fish miss. They do not. The flake that reaches the bottom of a community tank is sparse, half-rotted and nutritionally nothing like the meaty invertebrates a cory hunts, and a school expected to survive on it thins out slowly while the keeper believes they are being fed. Corys tidy nothing by design — they are hunters of the riverbed who happen to work downstairs. Feed them deliberately, as you would any other fish in the tank, with food chosen for them and delivered where they live.
What to drop: sinking staples and meaty foods
The staple is a small sinking pellet or miniature wafer that softens on the bottom rather than dissolving in the water column. Over the week, rotate in the foods that match the wild menu — frozen or live bloodworms and daphnia, dropped so they actually reach the floor. In a tank with greedy mid-water fish, feed the corys at lights-out or slip their food down along the glass at the front while the others are distracted at the surface. Aim for one or two feeds a day, sized so the school is still sifting eagerly after ten minutes but the floor is clean within the hour.
Substrate is part of the menu
How a cory eats makes the floor itself a feeding decision. On smooth sand the school sifts naturally, mouths working constantly, barbels intact. On coarse, sharp gravel the same behaviour wears those barbels down, and food falls into gaps no mouth can work — a double loss, because the fish is hungrier and its tasting equipment is damaged. If your tank has gravel, feed over a shallow sand patch or a smooth stone, and watch barbel length when you clean the glass: full, even barbels across the school are a quiet report card on both substrate and feeding.
Watch-outs at the bottom of the tank
Because the school feeds as a group, the fish to worry about is the individual who stops joining in: a cory sitting apart, thin behind the head, or with shortened, ragged barbels needs attention. Check that food is genuinely reaching the floor, test the water, and if the barbels look eroded or the fish keeps declining, an aquatics vet is the next step rather than a different wafer. On ordinary days the routine is easy to keep honest — in KinsLe, Care Teams lets the corys' sinking feed sit as an assigned daily duty, timestamped when the pellets go in, so the bottom of the tank is fed by name, not by assumption.