The Water clear removes substances harmful to your fish and keeps the water crystalline and odourless. It provides preventive action in the appearance of algae. Suitable for filter CF40 and Superclean 40 (bought before 2014), usually in the Ciano Aqua 15 to 30 and all Nexus tanks and all Cube tanks. Removes odour from aquarium water with quick and effective results. Contains activated carbon and is easy to replace.