ID this Crab

[fiji2000]

Can anyone help identify this crab? Friend or foe? He was a hitchhiker on some rock and I didn’t see him for the first several months. Seems to be growing larger. He is in a reef tank and seems to leave everything alone, I have only seen him eating Coralline, so far.

[astrong]

Looks like a common emerald crab, aka a mithrax. They are fairly harmless. And the yeat a lot of algae too.

[Instar]

A lot of hitchhiker crabs are algae eaters that get large and are very beneficial in the tank. If he hasn't bothered anything, judging from the blunt tips of the claws, he is an algae eater like an emerald. Although, no doubt, he eats different species of algae than they do.

[fiji2000]

Thanks for the quick reply. I did capture him and put him in my 1 ½ gallon Nano for about a week. Tonight I felt sorry for him and put him back in the 110. I have a book on Caribbean reef creatures, but was unable to identify him. Pacific maybe? What do you think?

[Instar]

I'd go for the pacific. Check for a family similar to the emerald but different species.

[scuba_steveo]

Red emeralds? I want some.

[MikeDeL]

Wouldnt a red emerald crab be.... a RUBY crab?? :o

[Ram_Puppy]

I have been wanting some red emeralds (pacific) and or some hawaiian strawberry crabs for a while... I am on a waitinglist at saltwaterfish for the latter, but that list has been going strong for 8 or so months now. :(