Filter-Pond Keeper 1.75 for 2500 Gallons19. 5" X 37" The PondKeeper media is so unique, there is no other exactly like it. Designed to protect sensitive beneficial bacteria during backwash, while providing huge amounts of surface area for the bacteria to live and prosper. The PondKeeper filter utilizes a totally unique backwashing jetting system we call the "FLUFF N SPIN" system. Not only does the internal design of the filter allow for a "FLUFFING" of the media during backwash, but spins