The Juwel Nitrax Filter Media for Aquariums reduces nitrate levels in your aquarium, resulting in significantly less algae growth. Nitrax is a biological filter that contains specialized microorganisms that break down poisonous metabolites (ammonium/nitrite) in your aquarium, lowering the risk of fish mortality and also promoting plant growth. Nitrax also reduces algae growth by anaerobically breaking down nitrate, thereby enhancing your fish's vitality.