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SeanySean
07/07/2007, 01:31 PM
Does anyone know what type of crab this is, can't get a better picture as it is camera shy! I found him after changing my rock around

http://i31.photobucket.com/albums/c355/seanmccarthy_/DSC_0912.jpg

I have watched him for an hour or so and all he seems interested in is algae so hopefully he is ok?

Sean

kau_cinta_ku
07/07/2007, 02:18 PM
herd to see him clearly but usually black pointed claws = not safe

SeanySean
07/07/2007, 02:25 PM
he does have those :( he is black and white on top in armmy type stripes and he has black claws if that helps

fatdaddy
07/07/2007, 04:36 PM
Could it be a porcelain crab?
http://www.saltwaterfish.com/site_11_03/images/181_porce.jpg

Just a filter feeder in that case.

SeanySean
07/07/2007, 06:59 PM
I wish... he is cool but not that cool, he looks safe, but I guess looks can be deceiving. he kinda likes the bit of LR he is on and eats the algae frantically from it. do bad crabs like algae as well as corals?

jaymz101
07/07/2007, 07:36 PM
Most crabs are scavengers and will eat whatever comes their way. Usually when young they will pick at algae and detritus, as they get bigger they may start nipping at corals, polyps, and the occasional fish. The exception is the porcelain crabs (one pictured above) are filter feeders.

JPagliai
07/07/2007, 08:00 PM
I found this thread on RC. I think this may be your crab...it was voted to be a black mithrax. Take a look at the pictures on this thread. Is this your crab?

http://www.reefcentral.com/forums/showthread.php?s=&threadid=551942&perpage=25&pagenumber=1

SeanySean
07/07/2007, 08:07 PM
Afraid not JP that guy looks far meaner than mine, his body is very mithrax shaped, but has waves of white on his shell, (you can just see them in the pic)

fatdaddy
07/07/2007, 09:09 PM
Set a trap. If it's carnivorous, you should be able to bag him over night. If not, I'd just wait for it to be a problem. No foul, no harm.

SeanySean
07/07/2007, 09:16 PM
I really dont think this guy likes meat as he is still in the spikey LR... many hours later! (just checked :) )h

JPagliai
07/07/2007, 09:19 PM
Well, I found a website that lists all the crabs in the same family as mithrax. This is the closest I found to your image:

http://www.flmnh.ufl.edu/reefs/guamimg/crustacea/xanthidae/Pages/Image45.html

SeanySean
07/08/2007, 05:25 AM
that looks like him :) take it he is good then?

reefing102
07/08/2007, 08:34 AM
if that is him he is a form of xanthid crab and they are very usually a bad crab - i forgot what makes them bad but most xanthids are bad

JPagliai
07/08/2007, 09:44 AM
Mithrax (emerald) crabs are part of the Xanthid family and all of them get mixed reviews in the reef hobby. Basically, they will eat anything. As for how reef safe they are, it all depends on what you have in your tank. They typically won't bother corals. Their appetite will grow as they do and they may start picking off your cleaning crew.

SeanySean
07/08/2007, 11:09 AM
I will keep an eye on him in that case he is very small at the moment so I will watch how he does over time, he is really cool though so do not want to get him unless I really have to. I have had Mithrax carbs before withought problems, however, they were red and green emerald types