If it is too high, the water is corrosive. If it is too low, it will cause scale build up. This form of chlorine will not kill algae or bacteria. The level of combined chlorine in your pool added to the free chlorine residual gives you the total chlorine reading. Chlorine - a sanitizer and disinfectant added to pools and spas to prevent and kill bacteria and algae.
Chlorine comes in numerous chemical forms and methods of application.
D.E. powder - diatomaceous earth. A white powder that is used as the filter media in D.E. filters. Free chlorine residual - the active chlorine level in the pool water after the chlorine demand is satisfied. Ionizer- introduces copper ions into the water to aid in killing algae and bacteria. A chlorine residual must still be maintained and shock treatments are still required.