Wazit? Please help identify this crab.

[helihead]

Hi all,
We have a 29 gal that has been going really well for about a year. We haven't lost a fish in at least 6 months. Our hermits and snails were doing well too. We bought 2 emerald crabs and a sally lightfoot. The sally ran off day one and we never saw her again. The emeralds were doing great and we would see them all over the live rock all the time. They never bothered anything and never dug in the sand.
One day we started to notice snail and hermit shells laying around empty. Everything else seemed fine. We saw more empty shells that started to pile up in the back corner behind the live rock and also started seeing sand pushed around and signs of digging under the live rock. We kept looking and eventually found the culprit. He is the same guy that is in my crabatar and in the two pics and we are not sure what he is.
He is over twice the size of our emeralds and he digs like crazy. We thought initially that maybe somehow it was the Sally all grown up but it doesn't move anything like one of those and we know we saw the hermits and shrimp dragging around parts of Sally (didn't look like molt). The emeralds hung out in the live rock but he lives under in burrows that he digs. The entrance to his largest burrow looks like something off dungeons and dragons with shells and carcases laying all around the entrance.
I never saw the emeralds eat anything except algea and occaisional flake but he eats everything including all the hermits and snails AND the two emeralds. We saw him totin legs back to his burrow. They were probably .75" wide just counting their bodies (not legs too) and he is twice that easily. I'd say with legs he is probably 2"-2.75" across and getting bigger every day. They were green and he is almost white with red tipped claws and markings as you can see.
Any ideas what type of crab this is?
Thanks!

 

[chana]

Gorilla crab? Regardless, IMO from what I've learned, any crab with brown pointy claws is BAD! Get him outta there! Had our own experience with a gorilla, same type of situation... pile of sand and tons of death. Good luck removing him. Hopefully for you he is under a rock that you can take out. Ours went way up into a hole the rock so we took the whole rock out and had to pull him out with tweezers. We gave him to a local guy who wanted him for his sump.

 

[btldreef]

That is a bad crab! He needs to be removed inmediately. He's killing off your CUC, and when he's done w/ them, he will turn towards your fish.
It looks and sounds like a gorilla crab.

 

[helihead]

Thanks for the input. We're about to switch up to a 43 gal tank and I think I will take that opportunity to get him out of there. Guess I will call around the local aquarium shops and see if they will take him since I hate to just whack him for doing what he was designed to do.
He was sitting right next to the glass this morning eating some algea I had dropped in and I got the ruler and measured him. He is easily over 3" and more like 3.5 when he stretches out. I looked at a bunch of pics of gorillas and they all seem to have fuzzy legs. He is almost completely smooth so I'm wodering if he is maybe a stone crab.
It's strange that he is absolutely terrified of the cleaner shrimp although it isn't half his side. He sees it and runs for his burrow. I dropped a small shrimp in for him and the cleaner shrimp actually took it away from him and he ran for his burrow.
The funny behaviour that we have noticed is how he interacts with our pencil urchin. I have seen him numerous time sitting really close to it. The first few times I though "OH no he is going to eat it". I watched closely and have seen him repeatedly appear to clean the urchins spines. He takes his claws and slided them gently down the spines and then eats something he is getting off his claws. The urchin seems totally unhurt and actually perks his spines up and sit still when it starts.
Anyway, thanks for the help.