Fritz Carbon AP is a high-quality, 4mm pelletized, activated carbon ideal for use in fresh or saltwater aquariums. Use 1/8 lb (approx. 1/2 cup) for every 20 gallons (78 liters) of aquarium water. The amount of carbon required may vary from system to system. Monitor the clarity of water and adjust the amount of carbon if necessary. For best results, replace carbon every two weeks as part of regular tank maintenance. To keep the carbon “active,” Carbon AP has not been pre-washed. Therefore, it is necessary to thoroughly rinse with cold water. After rinsing, place carbon in a filter media bag. Place in high flow area of filter to maximize water flow through the carbon.