SSalty
Team Liquid Force
It is whitish with red eyes. It's probably 1.5 inches. I didn't add it to the tank, it is a hitchiker.
Try googling xanthid crab. That's what it look like to me, but kinda hard to tell form the pic. I have one in my tank. Did great for quite some time then starting eating all me snails and might have got a fish to but don't know for sure.
Ssalty,
White and red leads me to think it's a porcelain crab. If you look closely at your pic, it shows (albeit with bad lighting) reddish/brown "freckles"....this is indicative of a Porcelain crab......
Ssalty,
The top pic shows dotted "freckles" on the crab.
Are they brownish red?
I didn't add mine came in on a piece of live rock I had it for a long time before I ever noticed it. I kept an eye on it after I found it and put it in my sump after all my snails and conchs started dying off real fast. I put it in the sump with a piece of softer very pourous rock and it actuall dug out a hole in the rock and lived in it.