Ecopower + Pond Filters are high performance filters with built in UVC.This filter will guarantee clearwater in ponds up to 4000 litres.Water enters the filter through a stepped hosetail (20/25/32/40mm). From here it passes into the UV chamber. The UV chamber features a \"turbulator\" to ensure that the water is exposed correctly to the UV light produced by the 6w UV bulb. This clumps the algae that causes greenwater together. The water then passes through a venturi to aerate it.The water passes into the bottom of the filter, passes through the biological media, and rises up through the foam filters. Waste in the bottom chamber can be desludged. The water exits through 32mm pipeworkThe biological media provides a home for friendly bacteria. These bacteria purify the water and remove fish waste. The foam filters remove debris and solid waste. When this filter is sized correctly, installed and maintained in accordance with our instructions we guarantee clear-water.