Crab found hugging my toadstool - guilty?

[Head-High and Glassy]

Found this guy hugging my toadstool and looking guilty as sin. Also seen picking at some of those tiny hard coral polyps that came in on line rock. On the other hand, he snatches hair algea and stuffs it down his mouth. So not sure. All i know is he looked massive in the tank but pretty pathetic and harmless now. Any idea on ID? Convict or acquit??

 

[Head-High and Glassy]

Here's the toadstool

 

[JustJordan]

To me, it looks like an emerald crab (Mithraculus sculptus). Many are harmless, but, many are also harmful. From my experience, it is about 50/50 whether they will play nice with coral and other inverts. I choose not to keep them in my systems to avoid this risk.

If they do choose to eat coral, fleshy LPS, or polyps are often their favorites. It is possible it has a taste for your toadstool as those marks look suspicious. He could be innocent though, as they do like hiding in crevices like beneath the "crown" of your toadstool.

There are some benefits to keeping them for some. They eat various algae including hair and bubble, and general detritus. Though there are often better inverts for these issues (besides bubble algae).

 

[StartingATank]

I don’t really think that it is a emerald crab as it is lacking the coloration of emeralds. I am not a crab expert, but I am 99% sure it is not an emerald crab

 

[JumboShrimp]