at that size I would just feed good flakes 3 to 4 times a day until they get larger and then move them on to pelletes. If you can get them started young on pellets you will have very healthy and colorful p's.
If they eat flakes, you have now just entered god status. If not welcome to the rest of the common folk. Brine shrimp always worked for me. But I would put in a big dumb lion head goldfish in there so the can pick at his fins. That way when they are ready to eat fish they will tell you by the dead carcass in the water.
first mistake I made was not trying flakes. My first reds were quarter size and they were raised on flakes and I changed thier diet to feeders. oh well, live and learn. Took me a while to get them to eat beefheart, shrimp, ect. because if it wasnt moving, they didnt want anything to do with it.
When my reds were small, I fed them normal tropical fish flakes, frozen cubes of mosquito larvae, pieces of shrimp, smelt, redfish fillet etc.
When they got a bit larger, small tetras to practice their hunting skills.