Chemical Aquarium Filter Media removes contaminants from your aquarium water that biological and mechanical filter media can not. These contaminants can come from fish medications, organic compounds produced by various biological processes, and pollutants in the air.
If you have an undesirable odor or color in your aquarium water, it's probable that chemical filter media will remove it. Examples of chemical aquarium media would include; activated carbons, zeolite and phosphate removers.