from what i understand soon as they hatch they are on their own... mom and dad just keep them safe from others and keep them from wondering off into traffic... but thats about it.. they dont make milk or chew food for them or anything... the fry just eat microbes and such...
so id say anywhere after a day or 3 (correction.. "Young are free-swimming about four days after hatching.")once they are all done hatching it would be safe to scoop/suck them out and put them a lil fry tank... dont forget to put a foam block on the filter intake so they dont get sucked up...
again this is just the way i understand things to be from my reading.. so if im wrong feel free to correct me