The BioStyle Activated Carbon Cartridge removes toxins and odors and improves water clarity. Optimize your BioStyle's filtration by adding this cartridge based on your aquarium's needs. Activated Carbon helps to remove cloudy water, harmful metals, odors, tannins or other colors for clear, pure aquarium water. Activated carbon is processed to have small, low-volume pores that increase the surface area available for absorption of unwanted substances. This cartridge fits inside the filter chamber, in place of the 30 ppi filter foam, of the BioStyle Power Filter series. The quantity of cartridges that can fit in a BioStyle unit depends on the size of the filter. Carbon should be used only when needed and replaced after 3 to 4 weeks, depending upon aquarium size, number of fish and plants, and declines in filter performance. Rinse cartridge with water before use – do not open the cartridge. Cartridge includes 50g of activated carbon.