Feeders are ok as a treat. I would ween the fish off live food to pellets or frozen. Vary it's diet. Give some frozen foods (raw shrimp, bloodworms, ect), pellets, live worms, etc. Feeders are known to cause disease because they are put under so much stress when it comes to shipping them in a bag by the 100+ and if any of them are sick, it'll trasfer to the other fish, especially if the other fish start picking on the dead one. So when your fish eats a diseased fish, it may very well get sick from that sick feeder.