Suitable for ponds of up to 10,000 imp. gallons (45,000 litres) with a maximum flow rate of 4,000 imp. gallons (18,000 litres) per hour. The new TMC 55 watt UV unit now has updated end caps and casing making the unit even more water tight than before! Using ultraviolet light, TMC UV units destroy the green, single-celled water borne algae which make garden ponds murky and unattractive. As no chemicals are used, there is no danger of pollution or over treatment of the water and sensitive plant and pond life is not affected. At the heart of each TMC UV unit is an ultraviolet lamp sealed inside a quartz sleeve. As water is pumped through the unit, ultraviolet light from the lamp destroys the algae, leaving the water clear. Features: Simple to install Easy to use Environmentally safe The main factors which govern the model you will need are pond size, flow rate, stocking level and the amount of sunlight the pond is subject to.