Food wise hikari first bites is the best IMO. If you wish to breed these again buy some liqui fry a small bottle that you put drops in your tank as soon as the eggs are laid, then feed with first bites after a couple of weeks.
In a couple of weeks you convicts might choose to breed again in which case they will lay eggs and ear any of there first fry that comes to close!!!! So if you want to keep them my suggestion would be to separate the fry