This extra large filter can handle a fish pond with 100,000 litres of water or a koi pond of 45,000 litres. Please note that this version is designed to be fed straight from a pond pump (A gravity/bottom drain version is also available). How It Works Dirty water is fed into the drum via the pond pump - as the drum rotaes it is forced out through the very fine mesh of the drum - the dirt can\'t fit through the mesh so collects on the mesh. A sensor constantly monitors the dirt build-up and periodically washes the dirt away via the waste drain. Hey presto - a self-cleaning filter that leaves you to get on with the nicer gardening jobs. Please allow 3-5 Days for delivery.