Let's not forget the thousands of possible pathogens that may be hitch-hiking on a amphibian. Likewise in the wild, most species of frogs DO NOT eat other amphibians commonly. There are a few species (C. cornuta is on that I can think of off hand) that actually DO specialize in eating other frogs/amphibians. These frogs though have enzymes that allow them to accomplish this without harm, because they have millions of years of evolution to allow that type of foraging behavior (similar to how king snakes can eat venomous snakes without harm). Plus I personally couldn't bare to watch a frog eat another frog. So stick to insects, and if you really must for a RARE TREAT pinkie mice.