i just went through this last week or so. The best scenario for me ,from the great feedback people gave was:
to get a syphon started near the bubble then dive in, and remove the bubble by hand. I grabbed the bubble and wiggled it loose, came right out. If the bubble broke I was going to use the syphon to clean up the bubble. The piece I removed was abouth the size of a marble. The outer skin was pretty rugged ,would have taken alot to break it. This so far has been my only bubble algae, that's what worked for me.
best of luck