Fluval Carbon is a premium bituminous-coal based activated carbon filter media crafted for both freshwater and marine aquariums. Its highly porous structure offers an extensive surface area for adsorption of dissolved organics, heavy metals, odours and discolouration, resulting in clearer, brighter and healthier aquarium water. Fluval specify that carbon should be replaced every four weeks to maintain peak performance and to prevent saturation from re-leaching captured contaminants.