You want to vary the diet, little ones will take brine shrimp, larger ones will eat crayfish, glass shrimp, fairy shrimp, etc. Most will eat small earth worms, some will eat superworms. crickets are good, and you can sneak floating pellets in while they are eating crickets or grasshoppers.
It might not be a great idea but mine got fros and wild caght fish, the fish were usually around the same size as any member of the shoal and for the singleton about 3", they also got purged in a tub of 2tsp/gal salt water for a week before feeding, I fed the ones over 6" everyother day. the more variety they get the more likely you are to avoid any dietary deficiencies.