Fluval Carbon Filter Media. Fluval Carbon is a premium, low-ash and highly porous carbon that is highly effective at removing heavy metals, odors, discolorations, organic contaminants and pollutants from aquarium water. Key Features : Chemical filter media Removes trace metals toxic to sensitive fish, organic contaminants, discolorations and odors Creates sparkling, crystal clear water Made of bituminous carbon - long lasting, highly porous and absorbent Provides large surface area for adsorption of impurities Will not raise phosphate levels Ideal for use with most canister filters For best results, replace every 4 weeks 3 x 100 g (3.5 oz) nylon bags or 1650g container.