4 x Compatible Foam and 4 x Compatible PolyMax ClearMax Filter Cartridges Compatible With Fluval U3 Internal Filter

You are buying a pack of 4 compatible Polymax / Clearmax filter cartridges and 4 x foam filters to fit the Fluval U3 internal filter. These help control green water and unsightly algae growth by adsorbing and trapping phosphate, nitrite and nitrate. It effectively produces crystal clear water, reduces odours, and creates ideal conditions for fish and plants. The polymax / clearmax filter cartridge helps reduce overall aquarium maintenance. The plain filter sponges contain the biological cultures, biologically and mechanically filtering the aquarium water. These cartridges should be replaced approximately every 4 weeks. Replacement PolyMax compatible filter cartridges for Fluvals U3 series of internal filters.