Dymax Anti-Ammonia Rock is a highly absorbent natural porous mineral composed largely of silica and aluminium. They are useful for their ability to capture and hold a variety of undesirable materials. This product is a chemical filter material that can absorb ammonia ions; nitrite ions and nitrate ions rapidly for the purpose of removing poisonous ammonia; nitrite and nitrate in water. Besides purifying it also helps to facilitate a more stable pH level and can reduce the frequency of water changes. The Dymax Anti-Ammonia Rock is an ideal product for use in any filtration system and suitable for all freshwater aquarium and pond applications. One 500g Bag treats 200L of water.