1. If you're worried about the frogs getting sucked up, you can put some pantyhose over the fliter intake. This should prevent any mishaps.
2. Crabs and lobsters WILL nip at and potentially kill small bottom dwelling fish. Not a good idea.
3. Are his scales also sticking out? If so, it's dropsy, and there's little you can do. However, if they're not sticking out, he could just be constipated. Try not feeding him for a few days.
4. If your angelfish aren't a pair, they could be agressive towards each other. If you CAN get a mated pair, however, that would be best.
5. All corys wink. They do this to force air into their gut, because in the wild, they live in poorly-oxygenated water. It sure is cute!
