Designed specifically for use with the API SuperClean 5-20 Power Filter, Crystal Bio-Chem Zorb Cartridges make your aquarium water clean and crystal clear. The exclusive research grade resin-carbon blend removes compounds that carbon alone cannot remove. Crystal Bio-Chem Zorb Cartridges are scientifically proven to remove organic pollutants including: discoloration, odors, heavy metals, and toxic gases which cloud water and degrade water quality. The double layered pads also remove fine debris to provide mechanical filtration. Crystal Bio-Chem Zorb Cartridges are not only filled with superior media, but they are also densely filled to provide even more filtration capacity. Features: Removes organic pollutants Used For: Aquariums Health Consideration: Makes water clean and clear Weight: 2 PK, Size: 10 Directions: Use when starting a new aquarium, when conducting regular maintenance to remove organic pollutants, or when colors or odors are detected. Replace monthly or sooner if aquarium is heavily stocked or as needed. Ideal for freshwater, saltwater, and reef applications.