I used to feed mine a lot of the gamma type foods you find in the freezer at your lfs. Bloodworms and brine shrimp etc.. If they take the flakes and things like pellets thats great because they are made to be really nutritous.
Also have a go with Hikari Carnivorous Food Sticks. I use these to feed my P, although he won't take them without stuffing them in prawns. Little baby P's will eat almost anything. They float too so they are easy to remove if they are not eaten.