Two quiet days living off the yolk sac
Newly hatched corydoras are barely more than a tail and a yolk sac, and for roughly the first couple of days that sac is all the food they need. They rest on the bottom, twitching occasionally, and your job in this window is simply not to disturb the conditions around them: shallow water, gentle filtration from a mature sponge filter, no strong current, and no tankmates. Do not offer food yet — uneaten food in the water now only feeds bacteria at exactly the moment the fry are least able to cope with poor water. Dim light and a calm tank are genuinely useful; the fry are prey-sized and wired to stay still and hidden, and a quiet start costs them nothing.
First foods must sink to where cory fry live
Once the yolk sacs are absorbed and the fry start nosing along the bottom, feeding begins — and placement is everything, because cory fry feed down low and will not come up for food the way many fry do. Microworms are ideal first fare since they sink and stay alive on the bottom for hours; powdered fry food dusted over their area and newly hatched brine shrimp, which also settle downwards, work alongside. Feed small amounts several times a day rather than one large meal, and aim the food at the patch of bottom where the fry gather rather than scattering it across the whole tank. A magnifier helps more than pride does: you are checking that bellies look faintly full, not guessing.
Shallow water, soft flow, and a daily siphon
Cory fry do best in water only a few inches deep at first, which keeps food concentrated near them and makes the whole tank easy to service. A bare base or a whisper of fine sand lets you see waste and leftover food, and a daily siphon with a length of airline tubing — gentle enough not to vacuum up fry — removes it before it rots. Follow with a small water change using water matched for temperature, added slowly. In a volume this small, yesterday's uneaten microworms are today's water-quality problem, and the fry are far more often lost to fouled water in week one than to any shortage of food.
The early risks are all about leftovers
The pattern behind most early cory losses is a bacterial bloom fed by overfeeding, which is why the discipline of small feeds and daily siphoning matters more than any particular food brand or gadget. Keep the sponge filter running constantly, avoid sudden large water changes that swing conditions, and raise the depth gradually as the fry grow and start ranging wider. Within a couple of weeks the survivors look like miniature corydoras, barbels and all, and the routine relaxes into ordinary grow-out care. Logging each day's feeds, siphons and water changes in KinsLe Care Teams gives the fry tank a written routine, so a helper's day with them looks exactly like yours.