Compatible for all canister filters.. 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. Mesh bag included for use in sumps and large filters for bulk sizes only