Meat is meat i guess, but Im pretty sure its not a good idea. I remember hearing something like this a while back, some guy wanted to use guppies or gold fish or something to feed his SW fish. I remember something about parasites that are harmless to FW fish, but can kill SW fish. So for this reason I would not recomend it. Besides, the whole idea of keepnig a SW/reef tank is to recreate the SW reef environment right? I doubt that you would find many tadpoles in a lionfishes home waters.....