573895 Superfish Aqua-Flow 100 Crystal Clear Refill Cartridge Filter cartridge for use with Superfish Aqua-Flow 100 Internal Filter. Crystal Clear Filter Cartridges include unique filter media with 100% open structure filter foam in combination with Norit Active Carbon, Clean Water, Zeolite and Active Alumina. Crystal Clear Cartridges remove all colouration, ammonia, heavy metals, nitrates, phosphates and silicates. For crystal clear water and the prevention of algae growth. 2 cartridges.