For use in custom sumps / refugiums, hang-on filters, pre filter boxes and more.Professional grade. Quick absorbing action with long term effectiveness.It can be cut to fit any size of your filter,Safe for both freshwater and marine aquarium.Zeolite coated Ammonia Minus Media removes toxic Ammonia - the number one killer of aquarium fish from new or established aquariums. Keeps aquarium water water crystal clear and ammonia free. Suitable for both freshwater and saltwater aquariums. Sealed to maintain freshness and prevent quality loss due to exposure to air.