Debbie, once you have a few in a tank it seems that they breed daily. I think its just that, with all the females in my tank, a different one is having a batch every couple of days so there are always 10 or 20 fry that are only a couple of days old. I don't bother separating them from the adults because the adults don't seem to eat as many fry as with most livebearers. I'm sure I'd have even more fry if I actually tried to protect them beyond just giving them some hiding places.