The SUNSUN CBF-350 koi pond filter system is a complete box filtration system designed to run pond water through a variety of filter media and fine and coarse foams to keep your pond looking crystal clear. This system is suitable for ponds with fish up to 1, 500 gallons or ornamental ponds up to 3, 000 gallons. Filter operation the filtration system uses a variety of filter media distributed amongst the different compartments inside its filter bay, allowing you to filter high volumes of water. This single-bay filter system has two (2) blue coarse filter foams and two (2) yellow fine filter foams included. The filter has four different stages of filtration: 1) firstly, the water passes through the filter media bay (stocked with media of your choice) 2) then the water is guided through high-quality Japanese matting, 3) after matting, the water will flow through the filter foams provided, 4) the last section of the filter bay has additional room for filter media.