Carbon Filter Media 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. Timing to replace the carbon filter media varies upon aquarium size, number of fish and plants, and declines in filter performance. This is replacement media for the BioCompact 50, FiltoSmart 200, FiltoSmart Thermo 200, FiltoSmart 300, and FiltoSmart Thermo 300. The Carbon Filter Media includes two replacement packets of carbon filter media. Each package contains 4.6 oz. of carbon filter media. Carbon Filter Media removes toxins and odors and improves water clarity. 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 Timing to replace the carbon filter media varies upon aquarium size and the number of fish and plants Carbon filter media is replacement media for the BioCompact 50, FiltoSmart 200, FiltoSmart Thermo 200, FiltoSmart 300, and FiltoSmart Thermo 300