The most scientifically-advanced filter media available. For sparkling clean water and healthy fish. Bio-Chem Zorb is a blend of 2 research-grade scavenger resins, 2 pharmaceutical-grade ion-exchange resins and high porosity activated carbon in a convenient filter pouch. Bio-Chem Zorb removes organic waste, toxic gases, water discoloration, foul odors and phenols in both fresh and saltwater, and toxic heavy metals in freshwater. Bio-Chem Zorb will not release phosphates. Treats up to 55 Gallons.