Time the food on the substrate
Corydoras are overfed when sinking food outlasts the feeding session, and the clock on the substrate is your clearest measure. Corys feed by snuffling along the bottom, mouthing sand and small morsels, and a healthy group finds and finishes a correct ration of pellets or a shared wafer well within the hour. Drop the food after the main tank lights dim, then look again before bed: pellets still sitting whole on the sand, or a wafer with only polite nibbles taken out of it, mean you offered more than the group could work through. Reduce by one pellet at a time until the bottom is clean within that hour.
Look for fuzz where the leftovers land
Uneaten corydoras food announces itself on the substrate within a day or two. Sinking pellets that miss the group soften, swell, and grow a halo of white or grey fungus as they decay between the grains — an unmistakable sign that food is reaching the bottom faster than mouths are. Check the corners and the sheltered spots behind plants and wood, where current drops debris and corys forage last. In a sand substrate the decay sits on the surface where you can siphon it away and count it; in gravel it sinks out of sight and rots between the stones, which is one reason so many overfed cory tanks smell stale when the hood lifts.
Watch the group's shape and energy
A corydoras group at the right ration is busy: fish shuttle across the bottom in loose company, barbels working, with regular trips to the surface. Overfed corys broaden — females are naturally rounder, especially when carrying eggs, but a whole group growing thick through the back and slowing down together points at the food, not the season. Compare today's fish against a photo from a few months ago rather than against each other, since a group overfeeds in unison and every fish looks normal next to its equally plump tankmates. Plump and lazy plus leftovers on the sand is a ration problem; plump and busy with a clean bottom usually is not.
Separate underfeeding the corys from overfeeding the tank
The classic corydoras mistake runs in both directions at once: too much food enters the tank, yet the corys still go hungry because faster fish eat at the surface first. If your corys are slim while food decays on the bottom, the problem is delivery, not quantity — the food is landing where and when the group cannot use it. Feed the corys specifically: sinking food dropped near their resting area after lights-out, when the day-active fish have settled, lets the group feed in peace. Judge the ration only by what remains after those targeted feeds, not by how much went into the tank overall.
When full bellies hide a different problem
Corydoras that stop foraging, rest on the bottom with clamped fins, breathe rapidly, or show worn or shortened barbels need more than a smaller ration — damaged barbels in particular are tied to fouling substrate and poor water, and an aquatic veterinarian or experienced aquatic shop should help you work out the cause. A group that suddenly leaves food it always finished is reporting something, too: test the water and look hard at every fish before assuming appetites simply changed. For the routine itself, KinsLe Care Teams turn your corydoras' evening feed into an assigned duty with the amount noted, marked complete with a timestamp once done — one measured drop of sinking food per night, whoever is on duty.