My fish get a variety of foods such as smelt, fillets, krill etc. but I do give them live food on occasion. They are larger enough to eat feeders now, just set up a 10G tank so you can quarantine them for a week or 2 to make sure they are free of disease.
I started giving my guys live food at about 2" and they went right for it.
Again, thier staple diet should be the things listed above, but a serving of feeders from time to time is ok, and very entertaining!!
For "feeders" I use things like danios, tetras, or whatever else the lfs has for a $1 each or so. Goldfish and rosies are not good cause they have growth inhibiting hormones, not to mention they are kept in horrible conditions that lead to disease.