AquaChek's Monopersulfate test strips allow pool and spa owners utilizing mineral-based sanitizing systems to test for potassium monopersulfate, an oxidizing agent found in mineral-based systems, pH, and total alkalinity simply by inserting the test strip into the water for 1 second, and seconds later you have fast, accurate results. It is recommended that you test your pool a minimum of twice per week, and spas before each use, to get an accurate picture of the health of your pool or spa.