Unknown crab that has significantly grown....

[born2chill]

My tank has been setup for 7 or 8 months abd I first noticed this hitchhiker a couple of months ago. I saw him again for the first time in a while less than a week ago and he has gotten huge. He is about the size of a dollar coin and his claws are pretty big. I hope he won't hurt anything in my tank. I lost a peppermint shrimp lately and am not sure if it is due to this guy. My hippo likes to sleep in a cave where I have seen this guy hanging out before, so I don't want to see my prized 5 inch hippo hurt by this guy.

 

[Fluff]

It's hard to determine the species but if you have a sump or fuge, that's where I'd put it. From the pic, it looks like he's hanging out around some zoo polyps? I'd watch them incase he's snacking. But, chances are, he's probably just plucking off your snails. Here is a link to a few pages of different crab ID's.


http://www.wetwebmedia.com/swcrabidfaqs.htm

 

[born2chill]

Thanks for pointing me in the right direction. It's sad to see that its probably a Predatory Xanthid crab. How would I go about removing him from the tank? I guess this is the reason I have been seeing quite a few empty snail shells lately and missing my pep. shrimp. I thought it was the heat since it can get warm in my basement and my lighting is pretty strong. I would really be upset if this guy would kill any of my fish. I'm especially worried about my yellow watchman and royal gramma since they're my smallest fish.

edit: Its funny you mentioned snacking since he seemed to be snacking on the rock, but I didn't specifically see him snacking on the polyps.

 

[Fluff]

If you got that pic, he's pretty brave. I'd just grab him when he comes out of the rock. If that doesn't work, you could use the glass trap. Tilt a glass against the rock you seen him in and throw some bait in the bottom. When he goes in to feast, he won't be able to get back up the smooth sides of the glass. It may take a few tries to catch him though. Good luck.

 

[born2chill]

The thing is he usually isn't out in the open like that. In fact, I was shocked to see him out and about like that. He was there long enough for me to get my digital camera, turn on my aquarium lights and snap about 10 or 12 pictures to get some usable shots. I have to give him credit for being so curageous. I'll try to get him out tomorrow since I need to pick up some more snails and would like to get some shrimp and I certainly don't want them to become lunch. I hope he comes out again tomorrow because removing rockwork isn't really a viable option for me. Do you have any idea how big a crab like this could get? He seems to have grown unbelievably quickly.

 

[Fluff]

Not sure how big it will get, probably a few inches. But, from my experience, the bigger they are, the braver they are. Good luck.

 

[Oceanicsublimat]

I have one of these guys.. they eat alot of algae.. hair on the legs, and scoops on the claws? They are the mithrax variety.. decorator crabs they call em.. I've seen mine scraping off the coraline algae and when I put in some nori he goes bonkers.. Good crab IMO..