SpaGuard® Spa Shock 5lb: This non-chlorine shock is the ideal oxidizer for spas with an ionizer unit. It makes undesirable compounds (body oils, lotions, sweat, etc.) disappear. Spa Shock is simple to use — just apply directly into your spa water while the pump is circulating. Fast-acting, this product allows you to return to the spa 15 minutes after application. This formula is pH buffered so its easier to keep the water balanced.