Carbon is a super efficient superior bituminous coal based carbon that is phosphate-free and adsorbs impurities, organics and pollutants._x000D_ Resulting in crystal clear, pure water. Use 1 cup (240 ml) of carbon for every 100 gallons (380 liters) of water._x000D_ Product will last several months depending on aquarium conditions._x000D_ Rinse well before use._x000D_ Place in filter bag and place bag where there is good water flow._x000D_ For best results, place after good mechanical filtration. Fine to use in all types of filter systems.