Zeolite Ammonia Remover is a natural ammonia-removing mineral for use in freshwater aquariums. It works well in both newly set-up aquariums to help prevent "new tank syndrome" and in established aquariums to prevent sudden "surges" in ammonia. Comes in a 6 1/2" x 6 1/2" fully rechargable pouch. One pouch treats 55 gallons. Pouches should be replaced every 1-3 months. Place pouch above filter foam pads.