The leftovers myth, dealt with first
The most persistent mistake with corydoras is believing they feed themselves. Because they nose along the bottom hoovering up missed scraps, they are sold as a cleanup crew, and in a busy community tank the scraps that reach them may amount to almost nothing — the tetras, barbs, and gouramis above have intercepted nearly everything on the way down. A corydoras needs its own deliberate feed: once a day at minimum, twice for youngsters or a large shoal. Starved corys do not announce it dramatically; they just grow thinner and quieter in a corner while the tank looks well fed.
Timing the feed for when corys wake up
Corydoras are at their most active from dusk onward, bustling over the substrate in a group, whiskery barbels tasting the sand for food. Feeding as the lights go down — or under a dim evening light — plays to that rhythm twice over: the corys are up and searching, and the day-active fish above are settling and less inclined to dive for sinking food. A sinking pellet or tablet dropped near the shoal's favourite stretch of open substrate will be found within minutes, and watching the group converge on it, tails up and noses down, is the confirmation the food arrived.
What belongs in a corydoras meal
Sinking pellets and small wafers made for bottom feeders are the reliable staple, softening in the water so the fish can mouth pieces off over a quarter of an hour or so. Corys are not algae eaters by design, so a pure algae wafer alone is a poor staple for them; they want the protein-rich fare of a small insect-and-crustacean hunter. Frozen daphnia, bloodworm, and baby brine shrimp, thawed and allowed to sink, are excellent additions a few times a week and trigger the most eager feeding response. Rotate a couple of pellet types so the shoal is not dependent on a single recipe, and break larger wafers so several fish can feed at once rather than one guarding the whole piece.
The sifting behaviour is the feeding behaviour
A happy corydoras spends its evening pushing its snout into fine sand and sifting mouthfuls, ejecting the sand through its gills. That behaviour needs the right stage: smooth, fine substrate lets them forage without wearing their barbels down, and feeding over a patch of open sand keeps pellets findable. If your corys must cross sharp gravel to eat, expect frayed barbels and half-hearted feeding — the fix is the substrate and the feeding spot, not more food.
Thin fish and other warnings
Judge your feeding by the fish, not the packet. A well-fed cory is plump when viewed from above, with a smooth curve behind the head; a ribby, hollow-bellied fish whose shoalmates look fine is being outcompeted or is unwell, and targeted evening feeds will separate the two causes. Food still sitting untouched an hour after lights-out, on the other hand, means the portion shrank or the shoal is smaller than the last time you counted. Corys kept hungry become shy and inactive, the opposite of the bustling group that makes them worth keeping.
A separate duty for the bottom of the tank
Because the cory feed happens at a different moment, with different food, from the surface feed, it slips easily: the tank looks fed because the top fish were. Listing the corydoras feed in KinsLe's Care Teams as its own evening duty, with the pellet type noted, keeps the bottom feed from being anyone's afterthought and gives the whole shoal a routine as deliberate as the meal itself.