After Shock is a chlorine reducer that is primarily used with Stain Solution #1, "The Iron, Cobalt and Spot Etching Stuff" to reduce the chlorine to below 1 ppm. After Shock can also be used to quickly lower chlorine levels after shocking, great for commercial pools!
Dosing: 2 ounces removes 1ppm chlorine from 15,000 gallons of pool water