Fluval Poly/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 odors, and creates ideal conditions for fish and plants. The filter cartridge helps reduce overall aquarium maintenance. It is ideal for freshwater and marine environments and designed for Fluval?s U2 Underwater Filter. Contains 2 cartridges Key Features : Filter cartridge helps control green water and unsightly algae growth by adsorbing and trapping phosphate, nitrite and nitrate Effectively produces crystal clear water, reduces odors, and creates ideal conditions for fish and plants Helps reduce overall aquarium maintenance Ideal for freshwater and marine environments Designed for Fluval?s U2 Underwater Filter Contains 2 cartridges Also available : A490 Fluval U2 Poly/Carbon Cartridge A486 Fluval U2 Foam pad A495 Fluval U2/U3/U4 Biomax,