Need ID on this crab

[nemonick84]

This little guy hitchhiked in on my Xenia. Lately I've noticed some of my polyps look a little frayed. Pretty sure this guy is munching on them.
Any help would be great.
Thanks

 

[nemonick84]

Sorry about the pics - kinda blurry.
These might be a bit better...

 

[nemonick84]

no one knows? hmmm

 

[dave11]

Maybe a swmming crab but front claws look a little long for that - picture is a bit blurred to tell- Thing is most if any crabs arent reef safe by a long mark
Dave