Pond Logic Activated Carbon, 9 lbs (w/ Mesh Bag) 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.