What is this mystery crab?

[msteane]

Found this guy hiding under a rock in my tank. Any clue whether he's good or bad? I managed to catch him and he's living in a container in the sump at the moment. The brown curvy thing is a feather duster worm growing on him. Not sure if the purple is actually a part of him or something growing on him.

 

[Duke]

looks like an arrow crab.. i think they arent totally reef safe but i dont know for sure.. google has a mixed opinion on that one.

 

[harleymike]

thats what i thaought too duke. I googled the image and it kinda looks like that

 

[TORX]

looks like an arrow crab.. i think they arent totally reef safe but i dont know for sure.. google has a mixed opinion on that one.

+1 for the arrow crab. I have read tons of reviews that say they are reef safe, but at the same point, there are just as many that say they have gone all Hannibal Lecter on their corals and even clams. I would not want one in my tank.

 

[msteane]

I also thought this at first.  The thing that makes me think otherwise is that arrowcrabs have as single 'horn', while this guy has two distinct ones.  I'll likely just put him in the sump to keep things clean in there.

 

[becca_vienna]

Some kind of decorator?
Mine likes to wear feather dusters... That one looks like a smaller version of the ones at Big Als in London!