Aqua One Phos-Nitra Reducer removes unwanted phosphates and nitrates to reduce algae and slime growth. Simply add to your filter or sump. Features & Benefits: Removes phosphate and nitrate build up from the aquarium water Re-useable media netting bag prevent beads from escaping and blocking the filter Phos-Nitra Reducer Beads are Ferric Oxide based. This help maintains low phosphate levels in your aquarium caused by overfeeding, poor quality fish food, lack of regular water changes and decaying plant matter Assists in maintaining clear aquarium water by lowering nutrients that algae feed upon Bead shaped for optimal water flow Suitable For: Coldwater, Freshwater Tropical