These are genuine replacement Clearmax Cartridges for the Fluval U Aquarium Filters. The Fluval U Clearmax filter cartridge helps 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 filter cartridge helps reduce overall aquarium maintenance. Genuine Fluval Part Helps control green water and unsightly algae growth Adsorbs and traps phosphate, nitrite and nitrate Effectively produces crystal clear water Reduces odours, and creates ideal conditions for fish and plants Helps reduce overall aquarium maintenance Available in 3 sizes to fit; U2, U3 and U4 Filters
