Aqueon Replacement Filter Cartridge The Aqueon Replacement Filter Cartridge is designed with the fish and the aquarist in mind. This filter cartridge helps to .enhance water quality and clarity, and increase oxygen levels with minimum noise. This patented Aqueon dual-sided replaceable dense-floss cartridges offer over 25% more activated carbon than the leading brands and have been designed to ensure even distribution of carbon throughout. Features: Ready-to-use, preassembled filter cartridges install in seconds Helps create crystal-clear, healthy water Patented dual-sided replaceable dense-floss cartridges filter out more particles and debris Cartridges contain more activated carbon to remove toxic impurities, odors and discoloration For best results replace cartridge every 4-6 weeks Remove cover from filter Remove used cartridge from bio-holster by pushing down gently on the holster and pulling the tab on the cartridge upwards Rinse new cartridge under cold water to remove carbon dust Insert new cartridge into bio-holster by aligning the key slot on the cartridge with the key slot on the biological grid Replace cover on filter Cartridges should be replaced every 4-6 weeks Item Specifications: Size: Medium Large