please help ID my crab !!

[kg4izw]

I got my aquarium a couple of weeks ago and there at least 2 crabs living in my live rock. I pulled one out and took pictures of it. It is the size of my pinky fingernail. It looks like a cross between a scorpion and a spider. I am not the best with the camera, and I could not figure out a file type that would appear in my post. SO, please go to my gallary and there will be 2 pics of the same crab I pulled out tonight.
I need to know if he is going to be trouble for me down the line with fish and corals, or if he is a vegiterian. Please let me know what you think. He is now living in a cereal bowl next to my tank.

[Mariner]

It's unlikely that anyone will be able to tell from your photos. Even if the pics were clear, it would be hard for even an expert to say with 100% certainty. You mentioned in your earlier post that the LFS said they were emerald (mithrax) crabs, and they well may be. But it's possible they could be look-a-likes that might be trouble.
FWIW,
Mariner

[H@rry]

If the tips of the claws have little flat places like a spatula you can be reasonably sure that it is a mithrax crab. Beyond that it is pretty much hit or miss. Most people want to get rid of all hitchhiker crabs. I caught most of mine using a tall drinking glass. I put a piece of shrimp rubberbanded to a little piece of rock in the botton of the glass and leaned it up against a rock. The crab slides down into the glass and then can't climb up the slick glass to get out. Do this after lights out and you may have them in the morning. If you don't want to kill it, put it in your sump.

[kg4izw]

OK, thanks for the advice. This one is going back to the store today. My wife says there is another one in there too. I wonder if the glass trick will work with a small fish in the tank competing for the shrimp tidbit also. But I sure like the idea. I gave the crab some new tank water this morning and put him in a plastic cup ready for the trip to the store.
Thanks for the crab advice, both of you.

[bergmmi]

.