Ultraviolet (UV) Sterilizers have been used in aquarium and ponds with regularity for nearly three decades. The main purpose of the units is to eradicate most free floating pathogens in the water passing through it, cleaning the entire tank in the process.
Free floating bacteria can present a huge problem in aquarium water. Whether it be a fatal bacterial infection spreading from fish to fish, or a more harmless bacteria which while multiply in the water can cause increasing cloudiness. An appropriately sized and correctly installed UV sterilizer will kill 99% of this bacteria.
UV sterilizers rarely focus on killing parasites. It’s important to note that fish diseases such as parasites are extremely common but seldom deadly. The UV would have to be extremely large (and more costly) in order to actually kill parasites, however when fish have parasitic infections, the true danger is what is known as a secondary bacterial infection.
This is how it works: First a parasite attaches to a fish and feeds on its bloodstream. After feeding for 24 hours, it will depart and multiply. Left behind is a tiny wound, perfect for developing a secondary bacterial infection, which can be fatal in as little as 24 hours.
Even free floating bacteria that isn’t a threat to fish can be a problem because it will tend to cloud water while multiplying. This can be observed as anything from a slight haze to a full-blown smoke screen, when you find yourself unable to see even an inch into the aquarium. If the latter phenomenon does occur, there is nothing other than a sterilizer that can resolve this problem. Even changing all the water may not work, as any remaining bacteria in gravel, filtration, etc., will resume to multiply. It’s easier to prevent this problem from occuring in the first place by installing a UV sterilizer that will help ensure constant crystal clear water.
One last cosmetic benefit of UV sterilizers is the reduction in free floating algae. This algae, also known as “green water” is not something any aquarist wants to see. This is a strain of algae that, rather than growing on surfaces such as gravel or aquarium glass, simply free floats and can make aquarium water look like pea soup. The UV is the only instrument that will kill any free floating algae and often can clean a tank in the worst condition within 24 hours.