API ACTIVATED FILTER CARBON clears aquarium water by removing organic waste, colors, odors, and dissolved medications. May be used in any aquarium filter as an all-natural means of clarifying water. Use when setting up a new aquarium, or in established aquariums, to improve water clarity. For freshwater, saltwater, and reef aquariums. May also be used in ornamental ponds. Use as directed on product label. With API Aquarium products, it’s easy to keep a beautiful saltwater, freshwater or reef aquarium. For over 50 years, API has been creating innovative, research-driven solutions that make it easier to care for your fish and aquarium.