Eheim Ehfikarbon is a high quality filter carbon, ideal for use with initial set-up of aquarium. It is mainly used in order to bind dissolved harmful substances and is pH-neutral. Before use, wash with hot water and rinse several times under cold water. Suitable for fresh water only. Place the material into the filter on top of the layer of mechanical filter media. If medications are being used the Ehfikarbon must be removed so that it does not absorb the medication.