I had some of it too in my tank. Added a Tang and it just disapeared. The fish just love it.

Well, he took care of a couple hairs of GHA while he was doing his rounds last night (or this morning before lights on) also, so I'm thinking he will single-handedly deal with any algae as long as it doesn't grow too fast. Until I get more rock (and a couple more crabs) at least.