Chemi-Pure is an excellent chemical filtration media that removes dissolved impurities; odors and dicolorations. In addition; it removes toxic heavy metals and keeps aquarium water crystal clear. Simple to use; it comes in it's own nylon bag. Helps keep your aquarium healthy by stabilizing pH and removing harmful ammonia and nitrate. Great for many applications; including power filters; canister filters; and wet/dry filters & sumps. Comprised of a mixture of activated carbon and ion exchange resins; Chemi-Pure can last up to six times as long as standard carbon. One unit of Dick Boyd's Chemi-Pure treats 5 to 40 gallons for up to 6 months!