Bubble algae are unsightly pests in saltwater aquariums. Algae have hold-fasts or anchoring structures and vesicles -- bubbles containing spores to produce more pest algae. Unfortunately, these algae thrive under the same conditions found in well-maintained reef tanks.
Removal
If you catch these algae early, your best bet is to manually remove them. You have to remove their entire anchoring structures or the algae will grow back. For this, you need some kind of scraping or poking tool. A sharpened screwdriver is an ideal tool for this. Take care not to pop the bubbles, since they contain spores that grow into more algae. You may want to have a siphon sucking out the algae while you scrape to make sure none manages to float away in the aquarium.
Denial of Nutrients
You can control bubble algae through denial of nutrients. Desirable macroalgae need the same nutrients as bubble algae and can suck them out of the water more efficiently, making it harder for undesirable algae like bubble algae to get footholds. Ornamental algae like Chateo and Caulerpa can look good in an aquarium or sump and work for this purpose. Coraline algae also compete well with bubble algae for real estate, forming a crust over surfaces that bubble algae cannot colonize.
Algea-Eating Inverts
Many marine aquariums employ various invertebrates to control algae. Snails often form the front line of defense against undesirable algae like bubble algae. Unfortunately, most common marine snails -- like turbo snails -- do a poor job of controlling algae. They may prevent bubble algae spores from getting footholds but cannot put a dent in a thriving infestation. Emerald crabs (Mithrax sculptus) and various sea urchins will voraciously eat bubble algae but will probably also eat expensive invertebrates like corals. Some sea hares will eat bubble algae and nothing else. Unfortunately, these sea hares will reproduce enough to eat all the bubble algae, then starve and die, fouling the water. Most algae-eating inverts have pros and cons.
Algea-Eating Fish
Some fish will eat bubble algae. Many species of blennies will spend their days picking at rocks, eating any algae they can find. Surgeonfish, tangs and angelfish will all keep bubble algae in check. However, most need a lot of space and can get aggressive toward other fish. All algae-eating fish require more food than just algae, since they will probably deplete the tank of algae relatively quickly.