calling all you crab experts! who am i?

[reefriot]

well i got an interesting hitchhiker on a head of stylophora i got from a friend. he musta been hiding out on the rock base as when i went to put the peice in my tank he floated off and scurried away before i could catch him. since then he has moved into the branches of the coral and is living there. never seems to leave the coral and doesn't seem to be harming it at all. heres the description.
he's a rusty brow with huge claws and a white patch on the back of his shell. he also has white bands on his legs and has red eyes. i've included a pic if you look just above the green leather into the branches of the stylophora behind it.
any idea if he is some sort of acro crab or if he just decided that this was as good a place as any to live. will he do damage to the coral? any info or help would be great. i seem to have 4 crabs in my tank total one is a mythrax(mean dude) i put there the other is a hairy white one(little guy) the other is a gray with blue eyes crab(small guy).

[Fiji Live Rock]

Get me a better photograph and I will know.

[Pineapple House]

Chances are that the crab you have found will not be a problem. Crabs found in heads of SPS corals are usually of the Family Xanthidae. They are typically commensals which sometimes protect the coral from predatory fish or invertebrates. All of these crabs should be watched carefully as not all of the Xanthids are harmless. Trapezia sp. (Family Trapeziidae) is usually found in Pocilloporadae while species such as Tetralia and Domecia (Family Xanthidae) are the typical residents of Acroporidae.(Delbeek and Sprung The Reef Aquarium, Vol. II, pg. 324). In the experience of the author and other reefkeepers that the author has conversed with, hairy brown crabs imported in SPS colonies tend to be harmful rather than commensal, while the tan, smooth shelled crabs are peaceful, well-behaved residents.

Here's a picture of one:
http://www.reefs.org/hhfaq/img/faq_acrocrab.jpg

PH =)

[reefriot]

hey thanks for the info, he is a smooth shelled crab and is kinda tan(dark tan/light brown). so far he hasn't even looked at anything else in the tank. my main worry was if he would do damage to the coral. i like to let my tanks behave the way nature does when it comes to the critters in there. so get tough or be eaten! just real touchy about animals screwing with my corals is all. i'll just keep an eye on him, kinda funny i was hand feeding my lawnmower tonite and i use an eyedropper, well i decided to see if the crab would go for it as when i usually just dump the food in the tank he clambers out to an outside branch of the coral trying to grab stuff but doesn't always get much. well he grabbed the eyedropper from me and started to pull it into the coral! was pretty funny looking.
thanks for the help
aaron