Um, I don't know how long those poor frogs will last. The piranha may not have eaten them yet but he may just have to figure out that he can. It can't be good for them to be picked up and dropped for fun either.
African dwarf frogs like to eat small live insect larvae and worms. They aren't as attracted to dead things but if they're hungry enough, they may eat some torn fish flesh. They won't eat scales, fins, or bones. If they did try to, they could choke on them. The frogs are attracted to motion like a wiggling worm. They will also eat frozen insect larvae and worms, perhaps attracted by the smell.
Pirahna should be fed more than just live fish. They can take earthworms and some of the pellets or other foods meant for carnivorous fish.
I just pulled this text of of this web site:
http://www.aquascapeonline.com/store/scrip...p?idCategory=23"Elongatus Piranha are one of the most aggressive piranha species. They are known to chase your finger from outside the tank. Must be kept in there own tank by themselves. They will kill anything you put in with them. "
Enough said.