Attacked, or falling apart?

[Joe Lydon]

So, this frag has been in the tank for awhile. Color is great. It sends out sweepers at night. I normally target feed as well (with pumps on). Well, last night I was trying to coax out the sun coral (still unsuccessful), so I turned off the pumps and target fed everything. Pumps were off for 15 minutes. I woke up this morning and noticed tissue damage. Did I do this by target feeding with the pumps off or does it look like something has been gnawing at it? Livestock = Nothing.. No fish. There is a monster emerald crab, hermits, some asterina stars and snails in the tank though.

As always, thanks for any advice!

Here's the damage.. It looks gouged in spots, there is some depth to it.

 

[riv]

My emerald crab started eating my acan so keep an eye on him.

 

[Joe Lydon]

My emerald crab started eating my acan so keep an eye on him.

Thanks! I will do that. It does look attacked, and not a disease/health issue, right? All of the damage was caused over an 8hr period. I have no experience with coral diseases, so I wouldn't know if this looks like something that could be health related.