The easiest way to keep your pond balanced is to install a filter and ultra violet clarifier. Fish waste will soon contaminate the water and sunlight will accelerate the growth of algae, turning the water green and unsightly. Adding a pond filter improves the pond stability and provides a healthy and clean environment for fish, plants and wildlife to thrive. The Bermuda UV Bio Box Filter 9500 treats ponds up to 9500 litres (2089 gallons) in volume. Complete with 11 watt UV clarifier, mechanical filter foams, biological filter medium and a stepped hosetail to fit 20/25/32/40mm diameter hose. Outlet pipe diameter 50mm. Dimensions: 38 x 28 x 48cm. 2 Year Guarantee (excluding UV lamp).