This Filtramax 12500 BasicSet pond filter from Ubbink is a complete filter set with numerous accessories and a UV-C pond filter for optimal results. It is a two-chamber biomechanical bank filter that has a built-in ultraviolet radiation (UVC) device in the housing. In addition, the filter evolves with the life of the pond, because it is expandable (or adjustable). This makes it perfectly and easily adaptable to the fish population and the amount of vegetation in small, medium or large ponds. Note: It should be installed at the edge of the pond, above the surface of the water or stream, so that the filtered water can return to the pond or stream without pressure. Ubbink recommends using the filter in combination with the Ubbink Smartmax 5000 pump (not included).