Tetra Pond Bio-Active Pressure Filter BP2500 is designed for ponds up to 2500 gallons. Bio-Active Pressure Filters provide mechanical and biological filtration to help maintain clear and healthy pond water. Its unique open profile bio-activators provide large surface area and unrestriced water flow to all surfaces for improved cleaning. It is designed with an easy, backflush valve for fast cleaning. UL listed and includes a 2 year limited warranty.