Mine hatched in 2-3 days at 25-26 degrees temp but people say it can take 4-5 days. Feed them after 24 hours. Best one I've used is Tetramin baby food. It doesn't foul the water and the corys grow on it just fine. Put it right at the bottom, don't sprinkle it at the surface as it will float. Good idea is also to put mulm from your filter sponges for the first week or two, they'll feed on the microorganisms in it. Don't worry about it looking dirty from it. Make sure they are in filtered/oxygenated place with no ammonia and nitrItes and remove left over food daily which normally looks like clumps on the sand. If they are in a breeder box, flush with tank water several times daily to keep the oxygen level and water quality ok because the holes don't provide enough flow. Pour tank carefully because the babies will be tiny/invisible. I cover the bottom of it with sand, small moss ball and fill it with floating plants to block the light.
As for the parents, it depends. Mine on average spawn twice every 10 days or at least have done so for the last 6 months, but there was a period of time when they were quiet enough.
Best of luck with it.
