I got a toadstool about a week ago and on the rock is this hard reddish purple something. I don't think it's coraline because it doesn't just look like it's encrusting, it looks like it's own entity. Any ideas?
Looks like a Honeycomb or Crust Coral. I can't really see the corallites that well. If you search for Favites Halicora (I think that's how it's spelled) or Leptastrea, one might match up.