API NITRA-ZORB filtration media is a ready-to-use pouch that can be added to your filter to remove ammonia, nitrite, and nitrate. NITRA-ZORB filtration media is made of natural and synthetic ion-exchange resins that selectively remove toxins from freshwater aquariums. NITRA-ZORB filtration media is completely phosphate-free and can be reused after recharging.