At what point can I add new fish to my existing fish. They are about 3 inches now and my older fish are anywhere from 6-12 inches. I don't want the little guys to be abused to death or not be able to get their fair share of food. I feed the big guys pellets and the little guys flake. Wait until they are on pellet? Also if I get new babies from the larger ones can they be added to the nursery tank with the smaller guys or do I run into the same issues I would run into that I mentioned before? I already killed off a bunch by stupidity, don't want to repeat the failure.