My lion head Elaine has been having some serious swim bladder problems and tends to get stuck in corners. Twice now I've found my apple snail too close for comfort when I came into the room. Today I couldn't be sure, but I think he may have been nibbling on her fin. Is it likely that he will 'attack' her if she can't move?? If so I have to get one of them out of there asap.

Chrissy

Separate them until you know for sure better to be safe than sorry.

Snails wont 'attack' perse, but they will crawl on any surface that they can cling to, and that includes a sick fish that can't swim away. Snails will eat the surface of the fish. I have seen a dead fish (it was a small tetra mind you) be completely eaten away by a pair of snails over the period of a day. So yeah, I'd separate your snail from your fish if it's motile-challenged.