Fluval U4 Filter Clearmax Cartridge

Amazon

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 Designed for use with the Fluvial U4 Underwater Filter 2 pieces of media

Amazon Marketplace

Provides effective chemical filtration Custom fit for the Fluval U3 Filter Traps fine debris, improves water clarity and removes impurities Easy to replace Works in freshwater, marine or reptile environments