Ceramic Bio-Filter Media with Vast Surface Area AND Open-Flow Porosity. Designed to improve upon deep sand beds or live rock to lower nitrates in marine & freshwater aquariums. Will also remove ammonia & nitrites. Use in sumps or in extra large filters.The product is from a naturally occurring pumice that can range in colors from white to light brown. A light film developing on the media is one of the keys to it working and is perfectly.Specifically designed to target ammonia and nitrite removal and minimizes nitratesnormal.Used in canister filters.Specifically designed to target ammonia and nitrite removal and minimizes nitrates