I have raised tons of cory fry. Mainly duplicareaus and eques. In my experience you will find you have some runts. I am a huge fan of feeding live bbs it makes their growth increase substantially. I also feed three times a day , the bottom will be covered in live bbs. After a few hours i will siphon all that is still left. The bellies of the babies will be noticeably pink. I do 80% water changes daily for the first 2 weeks. I hope that helps.