Ensure your Fluval G filter is operating at its best with Fluval G3 Chemical Filter Cartridge. There are three types of filtration that help keep your water healthy—mechanical， chemical and biological. Fluval G3 Chemical Filter Cartridge is part of the chemical filtration process and works with most loose or granulated chemical filter media like activated carbon. To keep your water clean and clear， media in the reusable Fluval G3 Chemical Filter Cartridge should be replaced regularly.