Fish do much better on live foods than on a flake diet. One of the very best id Daphnia, but the only thing is that you cannot collect it out of the wild like they did in the "old days" of the aquarium hobby. The water were they live is almost always polluted not so they are hard to get a hold of. but they are grow commercially and sold live by some LSFs. Another good choice is blood worms, fish love to eat these wriggle little beggers! My fish prefer live blood worms to another food that I give them. Also another GREAT live fish food is earthworms! these guys are often overlooked as a valuable food source for fish, mine love'em(even herbavorus fish will eat them)! if your fish are not big enough to take a whole chunck just cut them up, they are a good, easy, and costless method of live feeding your fish. Also another great live food is mosquito larvae, they are very easy to get a hold of, all you need to do is put a bucket(ice cream buckets work well) in a shaded, grassy corner of your yard or something, and they'll show up! The one thing you have to be careful of with these guys is not to put too many in your tank at a time, or you will have a house full of mosquitos! If you can't do any of these things LFSs usually have a great selection of frozen foods for your fish.