Bio Chem Zorb, a blend of resin and carbon filtration media, is composed of two research-grade organic scavenger resins, two pharmaceutical-grade ion-exchange resins, and high-porosity activated carbon adsorbents in a filter pouch. Removes organic waste in fresh and saltwater aquariums. Contains no phosphates. Removes toxic heavy metals in fresh water. Removes aquarium pollutants, such as toxic gases, water discoloration, foul odors, and phenols. One 10 oz. pouch treats 55 gallons. Easy-to-use pouch works three to six months. Directions For Use One 10 oz. pouch treats up to 55 gallons of aquarium water. Do not open filter pouch. Rinse pouch of Bio-Chem Zorb under tap water to remove any dust. Place pouch in path of water flow in the aquarium filter. Replace pouch every three to six months, depending on stocking density.