Hitchhiker on Acro

Got a new acro this weekend and noticed two crab hitchhikers. Don't have a pic yet but will try to get one. They are small, one about 1/4" wide at most the other smaller. Both are white with a black face. The black runs along the leading edge of the crab right across the eyes. Seem to only stay in the acro. Noticed this morning that one move over to another acro in the tank.

Are these guys safe or do I need to get them out of there??
ID would be helpfull also.

i read somewhere that there is a certain type of crab that hides in a SPS coral and the female intentionally gets itself stuck in the branches, and makes the male come to her to mate. just wondering if this is the same type of crab?? need pics to help with ID of these crabs. Although i think i read that these type crabs live in SPS's such as the birdsnest. So what type of acro is it ??

Typical Acro crab. I have three in three different colonies of acro. They are safe.

most seem to be trapeze crabs... very cool to watch aqnd seem in harmony with the acros.

are those the same crabs that i was refering to above ??

trapeze crabs are a very cool little addition to acros. I got one in on my last shipment, he is waayy cool. I spot feed him and he is a savage when I feed him,

http://melevsreef.com/id/acro_crab.html
Here a link I got form someone - I think that I got a good crab.

It's a trap crab.