I had no success with emerald crabs and BA. It ate my ornamental macroalgae, began stripping the coralline algae and then holed up in my galaxy coral and began eating it. Back to the lfs for that guy
Here's a recent thread on BA....
http://www.canreef.com/vbulletin/showthread.php?t=21746
I stand by my advice in removing each rock and chipping off a small portion of the rock where the BA is attached. Make sure the bubbles don't break while doing so. This is the ONLY sure fire, long term method of BA removal I have used, and I've tried 'em all.