Fluval Activated Carbon provides many benefits in both fresh and marine water. The high quality carbon provides a large porous area to trap minute particles. Besides providing a small sieve for mechanical trapping of organic wastes, carbon also removes liquid wastes from water. These include urine, dyes or impurities in solution. This action provides sparkling clear water in the aquarium. The large internal surface area also provides numerous points for important bacterial colonies to form and thrive. Carbon should always be removed during medication. It has also been recently noted that carbon will adsorb a large percentage of many of the nutrients in plant fertilizer products. As such, it should be used carefully when keeping live plants. Carbon loses its activity without outward sign. In general, carbon should be replaced on a monthly basis to ensure that active adsorption is maintained.