I concur, we need to know what type of fish you're thinking about. Livebearers do best on fresh hatched baby brine shrimp, while most egg layer fry are far too small to eat the same shrimp. Also with egg layers there are differing amounts of time you must wait to feed the fry as they have a yoke sack to consume. Once the yoke sack is gone they are free swimming. For my egg layers, I use good old green water as a first food. Between the green water and the sponge filter, my fish are ready for shrimp in just a few days after free swimming. Also, in a community tank the fish will eat any eggs that are laid unless it is cichlids and that doesn't always save them either.