Green toadstool problem?

[Voltekker]

I bought a small green toadstool at the Palm Beach Marine Aquarium Society frag swap and it was looking pretty good, but suddenly it looks as though my emerald crab might have taken a chunk off of it. It seems to be declining everyday and I'm not sure how to go about trying to save this coral. Any advice would be appreciated, here's a picture of the toadstool...

 

[tinyreef]

try cleaning the injured spot. sometimes injured flesh continues to rot without intervention, e.g. wave-action in the wild or hobbyist with turkey baster in the tank.

you might want to move it somewhere with more flow afterwards too. also, that frogspawn to its left might not be getting along with it (maybe it got zapped?).