Algreen"s pressureflo 2/000 pond filter with ultra-violet clarifier is the perfect solution to filtration for ponds up to 2/500 gallons. the pressureflo filters includes mechanical and biological filtration helping keep pond water clean and healthy. u.l listed with a 2 year warranty (excluding bulbs). this pond filter includes an integrated 9 watt uv bulb preventing formation of algae and making ponds virtually maintenance free.