Pooltester pH/O₂ measures the active oxygen content as well as the pH value.The tester includes two measuring chambers, which are filled with pool water. The appropriate reagent tablets are added to the test chambers to carry out a colour change. The discolored water is compared with the easy to read colour chart on the tester. Based on the values determined by the test, if necessary, adjustments can be made by adding the appropriate water treatment products.