Eheim ehfikarbon is a high quality filter carbon ideal for use with initial set up of aquariumr it is mainly used in order to bind dissolved harmful substances and is ph neutralr before use wash with hot water and rinse several times under cold waterr suitable for fresh water onlyr place the material into the filter on top of the layer of mechanical filter mediar if medications are being used the ehfikarbon must be removed so that it does not absorb the medication