This crab is very fast and very very skittish. The slightest movement outside the tank causes it to scurry away - quickly. It is extremely fast. Because it is so skittish it is next to impossible to get a good picture of this guy. These pictures of it attacking my Koralia powerhead are the best pictures I have been able to take of it so far. You need to click on the one above and zoom in on the one above to really see it.
Its claws seem to be smooth on the inside, lacking any serrations. It appears to be built strictly for eating algae. I have read some of the debate about crabs on line that tend to reply that the only place for Mithrax crabs, emerald aside, is in your refugium. I haven't seen this guy do any evil so I'm going to leave him in the tank for now. I don't think I can get him out even if I wanted to. Hopefully, he doesn't develop an appetite for toadstool leathers.