Bubble algae is considered a nuisance algae. Overtime, it can slowly cover the LR. The flipside of this is that it is usually very slow to cause a problem. The advantage of removing it while small is that if the bubble bursts, it will most likely release a lot less spores than if it grows larger and bursts. I wouldn't worry too much about small singular valonia. You could try a mithrax crab, although, many here don't like them. I owned two in the past..they DID eat some...and they stayed small during my ownership but they CAN increase in size and become opportunistic. SH
SH