need a crab id

[milmokes]

I have a crab in my tank that keeps eating all my fish. I dont know how to put a picture on here so I will try to describe it. It is brown with huge pinchers. It is about the size of half dollar. It has been in my tank for 6 years now and was a live rock hitchhiker. I have searched all over the web and can't find a picture or id on it. I also need to know how to catch it. It is fast and I have alot of live rock and am not sure which one he lives in. It 's body looks very compact as in the pinchers and legs are very close to the body. It is mean and ugly! Please help!
Tracy

 

[milmokes]

http://www.aquariumadvice.com/files/thumbs/t_pict2558__small_.jpg
I think I found him. What is he?

 

[Fluff]

Rock crab? They are very common hitchhikers. You could try a diy trap using a tall glass or soda bottle. Put some tasty vittle like fresh shrimp or fish, in the bottom and lean the bottle/glass against the rock you last seen him. Then hope he gets curious/hungry enough to go in. The smooth sides will keep him from climbing back out. Good luck.

 

[milmokes]

Thanks Cindy