Zeolite is a clinoptlolite filter media that removes ammonia from the pond or aquarium water. Can also remove by adsorption other potentially harmful molecules It also provides a large surface area for nitrifying bacteria in recirculation systems and can be used as a filter bed. Can be recharged several times overnight immersion in a salt solution (NaCl) or drying in an oven. Usage: Use 1 gram zeolite for every 1.5 mg of ammonia to be removed. For example, to remove 1 mg/l ammonia from 100 liters of water, use more than 65 grams zeolite (100 / 1.5 = 65 gram) For fresh water only (not effective in salt water). Dimension: 500g