This Size 6 API Bio-Chem Zorb Pouch contains a superior blend of resins and activated carbon for the most crystal-clear aquarium water imaginable. These active ingredients thoroughly remove organic aquarium pollutants - including colors, murkiness, odors, heavy metals, toxic gases and more - for improved water clarity and overall aquarium health. Additionally, these materials assist in the removal of light-blocking impurities, so they will help improve the growth of corals in saltwater aquariums and plants in freshwater aquariums. Bio-Chem Zorb will not remove trace elements from your saltwater aquarium. The Size 6 Bio-Chem Zorb Pouch is designed for use with aquariums up to 55 gallons. It is recommended to use this product in your saltwater or freshwater aquarium for super-clear water.