Fluval G6 Nitrate Cartidge Nitrate cartridge for the Fluval G6 Filter that helps to even out nitrate level in freshwater aquariums Long-lasting large capacity rechargeable ion exchange resin Quickly removes all excess of nitrate in a couple of days The cartridge can be removed once nitrate levels have normalized and then stored until required If canister is left in the filter it will maintain a low nitrate level for a period of time that is strictly dependent on the type of aquarium