wheat germ in spring and fall for sure. I also use mandu fu as a treat..great food to teach hand feeding.
Summer there is so much they can have out of your garden or grocery store. Peas, watermelon, cantelope, lettuce.
baby shrimp, crab, krab, earthworms. Rice, pearl barley (cooked please!)
I just try to feed a high quality food. I don't look for the cheapest stuff anymore as it is often a lot of filler. You ask 10 ponders what brand they feed and you are liable to get 10 different answers!!