The Rapid Dissolve Shock oxidize Tabs make dosing your spa with shock oxidizer (potassium monopersulfate) easy and fun! Just add 1 tab per 300 gallons once a week, or for heavily used spas, add 1 tab per 200 gallons twice a week. The tabs contain the same active ingredient as the Rapid Dissolve Stain and Scale control tabs and the Rapid Dissolve Alkalinity Increaser Tabs, creating a fizzy, exciting action upon application. No need to wait long for re-entry, as this product only requires a quick 15 minutes before hopping back in. Keep in mind, some test methods may show high total chlorine levels for up to 72 hours after use, but don't worry! One bottle of these tabs can cover 12 weekly applications in an average-sized spa.