AQUANATURE AMMO BLOCK instantly neutralizes ammonia, chlorine and chloramines, protecting fish and other aquatic life. Safe to use in planted aquarium. Ammonia is produced by decomposing plants, algae, fish waste and uneaten food. High ammonia levels often occur in new aquarium or in an established aquarium when adding new livestock, when a filter stops working due to power or mechanical failure or if existing beneficial bacterial colonies are lost due to the use of medications or sudden change in water conditions. AQUANATURE AMMO BLOCK will not alter pH or deplete oxygen levels. AQUANATURE AMMO BLOCK is a true complete water conditioner that not only neutralizes toxic ammonia but also the chlorine and chloramines found in tap water. It is extremely safe even when overdosed.