AquaClear Ammonia Remover Filter Insert contains a natural ammonia removing resin. This resin chemically bonds with ammonia to remove it from the aquarium water. Use of the ammonia remover insert will reduce and control toxic ammonia resulting in a healthy aquarium environment. For freshwater use only. Designed for use with AquaClear 20 (formerly AquaClear Mini) Power Filters. Shipping weight: 2/3 lb.