Activated carbon has the ability to support a denser bacterial population than sand or plastic beads. * It"s porosity, surface area, and surface roughness is unsurpassed for bacterial colonization. * Greater efficiency for the removal of biodegradable compounds. * Faster response to variations in water quality, such as concentration in biodegradable compounds, concentration in toxic organics and temperature. * Typically 4-6 lbs. will treat 1,000 gallons for 2-3 months. Each 9 lb bucket comes with one mesh bag.