I offer mine fish from time to time but not on a regular basis as I've heard they are hard to digest. Also my FBTs love an occasional meal worm or worms such as red wigglers or night crawlers that have been cut in half. Fruit flies are easy to raise and they sometimes like those as a snack. My FBTs will eat or try to eat anything that moves. But be careful when feeding them insects with hard shells because they can become impacted. I've had FBTs for 10 years with no feeding problems.