Crab Id!
 

I don't have my camera so no pic sorry. I have a couple crabs in my SPS corals there are very white like this page not see through and they have a very distinct black line through there face like they have a mask on are they acro eating crabs or some other bad crab? Appreciate the help

They are acro crabs. They are good. I believe they feed off of the slim the acro produces.

Yes, good. They will actually defend the coral from other types who might be hard on the coral.