JUWEL Nitrax reduces nitrate levels in your aquarium, leading to a considerable reduction in algae growth. Nitrax is a biological filter on the containing specialist microorganisms to break down poisonous metabolites (ammonium/nitrite) in your aquarium, thus reducing the danger of fish mortality. Nitrax also reduces algae growth by anaerobically breaking down nitrate, thus supporting the vitality of your fish.