Packed with special high performance resins, proven to reduce phosphate and nitrate for a cleaner, clearer aquarium and healthier fish. Thanks to the reduction in phosphate and nitrate the Fluval Clean & Clear Cartridge not only reduces algae growth but also tank maintenance by extending the time required between water changes. The Clean & Clear Cartridge is simply added to the central Fluval U cartridge alongside the Biomax and is suitable for all Fluval U Filters.