This product consists of special ion exchange resins which reduce the total water hardness in freshwater aquariums. The ideal total water hardness for tropical fish must be maintained under 8 °dGH - German degrees of hardness (approximately 14 °fGH – French degrees of hardness), whereas total water hardness GH of tap water is on average 11 °dGH - German degrees of hardness and often higher. MUTACAL resins activate an ionic exchange process which is the exchange of the ions in the water with other ions attached to the resins. This process lowers the water hardness in the aquarium to a safe level for the fish.