For use with freshwater aquariums only. Nitra-Zorb is a rechargeable ion-exchange filter media in a convenient pouch that fits in most filters. Great for starting new aquariums, Nitra-Zorb eliminates toxic ammonia, nitrite and nitrate. For use with freshwater aquariums only. Removes ammonia, nitrites, and nitrates, chemicals which are harmful to fish health. Also protects against ammonia surges. Designed to be used when setting up a new aquarium. Blend Of Natural And Synthetic Ion-Exchange Resins That Selectively Remove Ammonia, Nitrities, And Nitrates.: Size: 7.4 oz.