feeders are not a good idea to feed in excess, especially goldfish, since they can transmit deadly diseases, are very low in food value and high in fat, and actually prevent the proper metabolization of vitamin B1 (at least with goldfish). just though i'd throw that in there. tropical feeders such as guppies and danios, if properly fed and disease free, can make good occasional treats.
I feed the Ps I take care of from time to time various raw meats, including, chicken, pork, beef, and all manner of seafoods. they also get feeder guppies once a month. I try to feed something new daily.