Shock treat your pool at least once a week to kill unwanted bacteria and algae and to give your pool the boost of chlorine it needs to keep your water clean and clear hth. Ultimate shock treatment is a multipurpose sanitizer that provides brilliantly clear water controls algae clarifies water dissolves fast helps prevent stain and scale and softens water. The burst of blue leads to clearer cleaner water Visible Blue Action so you know it's working!