A healthy corydoras diet begins with a correction: these fish are not a clean-up crew that can live on whatever the other fish miss. Corydoras are dedicated bottom foragers from South American streams, spending their days in a companionable shoal, shovelling through sand with their barbels in search of insect larvae, worms and small crustaceans. A diet that respects that design means sinking, protein-aware food delivered deliberately to the substrate, in enough quantity that every fish in the group eats, not a hope that enough flakes drift down.
Why leftovers are not a diet
Flake food is intercepted at the surface and midwater, and what does sink is picked over by every fish in the tank on the way down. A corydoras relying on the residue gets the least nutritious fraction of the day's food and gets it irregularly, which is how well-kept tanks end up with thin cories while the surface fish thrive. There is a second, quieter issue: corydoras find food by smell and by working the substrate with sensitive barbels, and they feed most confidently in the evening and in a group. Feeding them properly is therefore about placement and timing as much as ingredients, putting a real meal on the bottom when the shoal is ready to work it over together.
The sinking menu a corydoras needs
Small sinking pellets or mini wafers formulated for catfish are the right staple, made to reach the floor intact and soften at the pace a grazing shoal eats. The protein side of the menu should rotate through frozen bloodworms, daphnia, blackworms and finely chopped earthworm, all close matches for the larvae and worms a wild cory spends its day extracting from sand and silt. Soft gel foods and blanched vegetables such as zucchini are eaten with interest too, though vegetables are a supplement for this species rather than a pillar. Live foods, where available, produce the finest sight in a cory tank: the whole shoal heads-down and busy, tails wagging, working a patch of substrate as a team. Whatever is on the menu, it must arrive in pieces small enough for a modest mouth.
Feeding the shoal, whole and at once
Corydoras are social feeders, and the group needs feeding as a group: scatter the sinking food across the area the shoal favours rather than dropping it in one guarded pile, so subordinate fish are not shouldered aside. An evening feed, after the day's surface feeding is done and the tank is quietening, lands best, with portions sized so the bottom is cleared within an hour or two. Any food still sitting untouched the next morning means the portion was too large or the food is being refused, both worth knowing. Sand rather than coarse gravel under the feeding area protects the barbels the fish feeds with, and a clean, well-oxygenated bottom matters because this is the layer where the shoal lives and eats.
Condition, barbels and the limits of diet
A well-fed corydoras is a rounded, busy fish with whiskers of full length and a shoal that spends the day in cheerful activity punctuated by rests on the sand. The classic warning signs are a hollow belly, a pinched look behind the head, and barbels worn down to stubs, which point to underfeeding, poor substrate or deteriorating water at the bottom of the tank, in some combination. A cory that stops feeding, breathes rapidly at the surface, or shows redness around the barbels and belly needs more than a menu change: test the water promptly and take advice from an aquatic veterinarian if the fish does not respond. Adding the cories' evening feed to the household routine in KinsLe lets Care Teams make sure the bottom of the tank is fed as faithfully as the top.