Monopersulfate is an oxidizing agent used in mineral purification systems. To test, just dip your AquaChek Monopersulfate strip into your pool or water for a quick second, and remove it immediately. You'll get results in just seconds.
To keep your pool at its best, test at each end a minimum of twice a week, and test your spa before each use. It's also a good idea to write down your results each time you test.