The PondMAX Automatic UV pressure filter 50000 is designed for large ponds, we recommend it for ponds up to 20,000 litres (fully shaded with no fish) or up to 10,000 litres if you are housing fish. This automatic pressure filter contains mechanical, biological and UV filtration components. Sponges and biomedia inside the canister catch suspended debris, over time, beneficial bacteria colonise this space and will provide biological filtration as well. A UV compartment housing an ultraviolet globe will keep your water clear and prevent algae blooms from turning your water green. scroll down for in depth info and specifications