They'll eat anything that drops into the tank. Which is why I have it well covered, and going to have to start weighting the lids down too. The white one (Frick) has a habit of "popping" the lids up when I walk into the room to let me know he's hungry, which is all the time. lol
I've seen them try, and they just spit it out. Besides, if they ate their own, I wouldn't be siphoning as much sh*t out of the tank as I do! LOL Not to mention be making millions on the most low maintenence fish alive!