For freshwater use only. Filters ammonia, nitrites, and nitrates from water. These chemicals are harmful to fish health. Also protects against ammonia and nitrite surges. Designed to be used while setting up a new aquarium. Water Filtration Media That Removes Ammonia, Nitrite, And Nitrate. Blend Of Natural And Synthetic Ion-Exchange Resins That Selectively Remove Ammonia, Nitrites, And Nitrates.