Unknown crab

It appears that I picked up a crab as a hitchhiker at some point.

Its black (or v dark colour) currently only has a leg span of roughly 1" and has a v low profile (body looks like its is only 1/8 thick at most). Very fast mover and hides well. Saw a glimse of it a couple of weeks ago but not again until now when it was hanging on the underside of a rock.

Didn't have time to get my camera out before he ran off but will try to get a photo if I see him again.

Am almost certain that its a bad thing to have. Any advise on how to catch would be appriciated.

Thanks

 

Just saw it again.

Its legs are black and white striped and its body is mottled.
Managed to take a couple of pics. Will post in the morning when I get to the office (left the USB lead for my phone at work).

 

Sounds like a Sally, but under different colors. Luna

 

Never really heard of a "good" hitchhiking crab. :-/

Just about always killers one way or another...

One way to try getting out....just put a small glass in the bottom close to a rock that is near with some frozen food submerged in the bottom of the glass. Crab crawls in, can't crawl out.

Another is build a miniature crab trap with some mesh netting/fishing line...bait it and wait.

Took me hours to get one out of my tank once upon a time.

Turned out to be a gorilla crab. deadly. tore my feather dusters to shreds.



Good Luck!

 

Thanks guys, will try the glass trick first (sounds easier)

Here are a couple of (bad) pics of the evil looking little git. Hes hanging upside down under the rock in the centre.

 

I would agree with you luna it's a sallt light foot.
Must have hitchhiked in on a rock at some point .

 

Definately a Sally. Pic at Liveaquaria looks just like it.

Saltwater Aquarium Invertebrates for Marine Reef Aquariums: Sally Lightfoot Crab

Thanks for your help guys.

Karma to Luna for ID based on my crap description and Karma to Omard for trap info. I'm going hunting

 

i often get black Mithrax on LR, from your description ( very black, mottled body) it sounds like the same beast.

Google the emerald crab and look at the ends of the claws, i would wager they are similar to your mystery crabs.

IF they are the black mithrax (no idea on the specie name) i have found them to be quite reef safe and a good eater of algae, i wouldn't trust them with some LPS and some Softies though.

Defo one for the sump if you have it, brilliant CUC.