I just got my guys off feeders and they are about 8". I think it is better to wait until they are more mature to change their diet. Get them some disease-free guppies, rosy reds or anything else you can catch (fatheads, crappie minnows) they will crush them as soon as they hit the water. Don't just dump them in all at once though. You have to train them to hit whatever hits the water, that way you can get them on krill and food sticks later....hope this helps