Bubble algae, of the Valonia variety, can be more than an interesting green bulb growing on the side of your coral frag or on the rocks. It can actually be a ruthless nuisance algae that becomes impossible to get rid of. As its name suggests, this type of algae grows in small bubble-like structures that trap in a little air and water, causing them to float if broken loose. This allows small bubbles to flow freely throughout the aquarium, and when they settle in, they reproduce like crazy. Some hobbyists urge others not to pop the bubbles during manual removal for fear of letting countless Valonia spores back into aquarium. Others swear by emerald mithrax crabs and other bubble algae eaters to do the job, but those critters often disappear shortly after their introduction. The best way to get rid of this type of algae, honestly, is to never get it in the first place, because no matter what you do, the algae seems to always follow. Always check coral frags for bubble algae, and Aiptasia for that matter, before putting them into your aquarium. If a bubble does break free, however, try to catch it in a net before it has a chance to repopulate the surrounding rocks with more. It’s a meticulous process to do it by hand, but with the unreliability of invertebrates, it’s really the only thing to do, short of tearing the tank down in order to clean the rocks.