i have always preferred to feed a staple diet of prepackaged food eg hikari sticks or the like, and then offered "treats" in between, of shrimp, meat, insects, feeder fish etc, depending on availability or how generous i am feeling. after all, prepackaged food is designed specifically for the fishies optimum health.
i find that feeding them too many "treats" tends to make them go off the prepackaged foods. so in my opinion it's best to feed them around 75 - 80% quality prepackaged foods and the rest made up of "treats". if they start going off the prepackaged stuff, i'll stop with the treats until they start eating it again.