Aspen Aeration 9 Inch DiffuserThe air diffuser base hold the diffuser firmly at the bottom of the pond while keeping the membrane up out of the mud. The hollow diffuser base is designed to be filled with sand or gravel. The 9 inch EPDM disc diffuser is designed for industry heavy duty installation. The ultrafine slits in flexible membrane diffuser are designed to release uniform bubbles for optimal oxygen transfer efficiency. These diffuser offer the lowest back pressure in the