This product reliably binds all hazardous substances in the water, thus keeping the little protégés alive and well. I agree with the other users to fully. Contradicting I have only the experts, which the chlorine would be outgassing. Chlorine as Cl2 occurs namely in gas form, in water it dissoziier contrast to 2Cl- and is so stable in water and must, therefore, as well as the ions of heavy metals and nitrite and nitrate, are brought into harmless compounds. The finished product of this reliable and long lasting, so that the fish can enjoy a long life with regular water changes and good maintenance.