I live in a colder climate and I never see algae blooms so I don’t need an UV system, plus they are expensive and use a lot of energy.
Whether you live in a warm or cold climate, a properly sized UV system is beneficial. UV systems use very little electricity and you likely would not even notice any savings on your electricity bill without one.
New ponds are especially prone to algae blooms until the whole ecological system of the pond matures, which may take several years. Ultraviolet lights are designed to kill any algae floating in the water. Algae blooms in ponds can turn a perfectly clear pond into a thick pea soup looking pond in a short period of time. The way ultraviolet lights work is when the algae, in the water, passes through the unit it is exposed to a very bright ultraviolet light. This energy from the light destroys the DNA in the algae which in turn causes it to eventually die.
As the algae cells die they will begin to stick together so that they can be filtered out of the water. Selecting the proper size light is very important. If the light is not big enough for the pond you will notice almost no effect. Additionally, if the water flow through the light is too fast, it will also reduce the efficiency of the light to where it has little effect. Ultraviolet lights are not effective against string type algae because it attaches to the pond and does not flow through the light.
Most manufacturers’ ratings are based on when the lamp is brand new and fresh. If you were to size your UV unit according to those numbers you would quickly notice your pond turning green and would be disappointed. From what we have found, UV lamps lose about 40% of their power in the first year. If you size the UV unit to where it can handle your pond gallonage running at 60% capacity of what the manufacturer says, you can then get about 1 year of life out of the bulb before replacing.