Wee little crabs living inside coral

[madducks42]

Picked up this Christmas Favia frag a couple weeks ago at a local frag sale and it’s chuck full of hitchhikers. It has some feather dusters on the side which from what I’ve read are harmless. But there are also some things living inside the coral. There are a couple little holes scattered around it and during feeding time little tiny crabs stick their claws out to grab food. Based on their size and pink claws I’m guessing they’re some type of acro crab? I can’t tell what’s in some of the other holes. The circle with the arrow pointing at it is where one of the crabs lives. The other two circles are around the mystery hitchhikers. Not the best picture because they’re so small but i haven’t had a chance to take a photo with my macro lens. Any guesses as to what the mystery spots are? Is the crab likely an acro crab and will it do any harm? The coral seems to be perfectly happy and healthy even with all the hitchhikers on it.

 

[Lovemyreef2015]

Where the arrow is, is probably a gall crab

 

[Brew12]

I agree, it is most likely a gall crab. People have mixed feelings about them being good or bad.

 

[madducks42]

Thanks all! That does indeed sound like what it is. I think I'm inclined to leave it since the frag seems to be doing just fine.

 

[KJ]

Coral hermit crab (Paguritta sp.) and coral barnacle (Pyrgomatid) harmless