From what I gathered, fish are a "treat" type of prey item, as are rodents. Nightcrawlers, roaches, and crickets are a good staple diet for them. Fish carry parasites, and can cause more harm then good. Rodents are a better "treat" and are just high in fat. Typically they don't carry any parasites, just make sure to get them from a reputable store. Some places keep their rodents in horrible conditions.