Product Description:JUWEL Carbon Sponges absorb odour compounds and turbidity as well as toxic compounds in your aquarium, leaving the water crystal clear. The fact that active charcoal in the form of a sponge is used guarantees even flow conditions for the filter medium, creating a very large and therefore highly effective surface.Due to these characteristics JUWEL charcoal filters are also perfect for filtering out residual medication after treating your fish.