The Fluval AquaClear Freshwater and Saltwater Active Carbon for AC20/AC30 Aquarium Power Filter is designed to improve water clarity by removing odors, discoloration, and impurities from aquarium water. Each insert is filled with high-quality activated carbon for effective chemical filtration in AquaClear 20 and 30 filters. These Active Carbon Filter media inserts help maintain clear, odor-free water and a healthy aquatic environment in both freshwater and saltwater aquariums. Available in Singular and 3-Pack Option