When they first start free swimming the best thing is frozen baby brine shrimp. Once they get a little size I make a fry food from crushed flakes crushed freeze dried krill crushed spirulina flakes and whatever else I can crush small enough. Another great product is the tiny Spectrum pellet called Grow. It comes in a .5 mm pellet. They can usually take this in about 2 weeks and they grow like crazy on it. Keep varrying thier foods and change water if you want them to grow fast.