They are not very fussy eaters but they do seem to enjoy variety. Almost anything is good but I especially like cabbage. Dont forget to add nuts to your list. I throw in whole unshelled peacan nuts (I have a tree) because I love to hear them crunch away and they seem to play tag with each other over them since they float but even peanuts are good and really cheap.
My pacu is a huge fan of spinach, I put alot of it in my fish food receipe mostly for the pacu. He also likes peas, grapes, cucumber, and amen to the unsalted peanuts. Altho if it hits the water the pacu will eat it so its not like it matters much what it is