If your bubble algae looks like this, I would suggest not getting the emerald crab - mine did not like it at all (unless you just like them, which is fine. I like mine but it doesn't do much except scurry around and eat coralline.)
http://reefkeeping.com/issues/2002-02/hcj/...es/image002.jpg
Borrow a flathead screwdriver, remove the rock (I put mine in a cooler to catch the drips - you could use a bowl since the rock is prob small) and take it to the kitchen table. With a good light shining on the rock, use the screwdriver and gouge the rock behind the bubble and make sure to get the bubble and what connects it to the rock. Take a decent divot out. What you do not want to do is pop the bubble. I tried it on one rock and it has grown throughout my tank to huge proportions.
If you have another pint of saltwater made, you can use a turkey baster to blast the rock clean. You may need to repeat as you see it come back.