Hitchhiking crab - ID please

[alex.parker]

This guy showed up with some corals. About 1.5 cm across, very hairy legs? Any ideas what it is and whether it should be left or removed?

 

[Moonstream]

looks like a mithrax crab. Id take it out if you value your inverts and fish. as they age they tend to get very aggresive, best kept in their own little tank.

 

[J. Montgomery]

I'd also say its an emerald (Mithrax) crab, but I say keep it. I have three of them in my 55 gallon. Some will eat bubble algae.

 

[clutch]

bad acro crab mithax indeed

 

[LeslieH]

The bad acro crab is Cymo (there are several species). The carapace is bumpy all over and the eyes are distinctly light blue. Id' say Moonstream & Josh are right - this is an emerald Mithrax that just wandered onto the acro. The majority of people who have posted about emeralds say they're algae & detritus eaters that don't harm a thing. The diet of crabs and other crustaceans change as they get larger. Occasionally a rogue small one will go after corals or something valuable but it's usually the really big ones with big appetites that become a problem.

 

[alex.parker]

Hmm, consensus seems to be Emerald mithrax. I think I'll leave him for now and monitor. The coral he was sitting on for the photo (actually a Seriatophora birdsnest) shows no damage...

Thanks for the input!

 

[GreyHawk1968]

It's an emerald Mithrax. Mainly herbivores. Have been known to consume bubble algae and hair algae. I've had several for years and no ill effects. I keep LPS/SPS .