The Lifegard Aquatics Carbon Filled Bio-Mate Media Balls are a great way to add carbon to a wet/dry filter, corner filter box or a canister filter. Each of these 1-1/2" diameter balls contains pelletized carbon. The truly economical person with a bit of time on their hands can actually open the balls and replace the carbon with bulk carbon such as the Inland Sea Pelletized Activated Carbon (carbon should be replaced monthly). For freshwater and saltwater aquariums. Contains approx. 1 pound of pelletized carbon. See the Data Sheet for ideas on how to use and combine with other Lifegard Aquatics Bio-Mate products.