Ultraviolet (UV) sterilizers are used to sterilize the water as it passes through a cylinder with a lamp that emits ultraviolet C light. They are used in aquariums and ponds to kill green water algae, parasites, bacteria, and viruses in the water column.
With the adoption of LED lighting systems, aquariums receive much more light than they did under standard fluorescent, making green water algae blooms more common. Planted tank hobbyists should consider adding to the system to prevent or cure a green water algae problem.
The effectiveness of a UV sterilizer has many factors, including flow rate, wattage, water clarity, and cleanliness of the quartz sleeve. Manufacturers of advanced and professional UV sterilizers will provide a guide on the recommended flow rate through the unit to kill green water algae, ich (Ichthyophthirius multifiliis), and bacteria.
A short dwell time of exposure to UVC light will kill green water algae. Many UV sterilizers (often having a built-in filter) are intended to work as clarifiers and are economical for preventing and killing green water algae and bacteria blooms.
A properly sized UV can prevent ich from reaching epidemic proportions and, in time, help eradicate the parasite from the aquarium. A UV sterilizer should not be used as a substitute for a quarantine system.
A UV sterilizers can be installed with a canister filter, sump-style filter, or powerhead with a prefilter. Installation is easy; all that needs to be done is to cut a return line tube and connect it to the in and out fittings on the UV sterilizer. Adjusting the flow through the UV sterilizer can ensure that all the parasites, bacteria, and viruses in the return line are killed.
UV sterilizers are low maintenance; they only need the bulb changed and periodically wipe down the quartz sleeve. Bulbs may need changing every 6 to 18 months, depending on the type of lamp used.
If mounting a UV sterilizer in a cabinet, ensure room for maintenance. The unit also needs to be mounted, so there is no air in the tube when operating. If mounted horizontally, the inlet and outlet should be pointed up, and if vertically mounted, fill from the bottom up.
UVC light should not be used on systems with added chelated chemicals or fertilizers, as it will destroy the chelation. UVC light should be turned off when treating the system with medications.
Hobbyists should never look at a lit UVC lamp outside its protective case as it can cause blindness and burn skin.