The colors, especially PH indications do not agree absolutely in line with the scale. Every aquarist knows the simple color tests, but this is even worse. A comparison with a calibrated pH tester also gave false readings. If I can "advise" between pH 7.0 ud PH 7.8 only - like here, then I do not need a tester. The tablets chlorine testing are crumbling with me after a few weeks in the packaging -without Fremdeinwirkung- and were no longer usable. My tip: digital pH tester (probe) buy ... purchase at a pool in the medium-effective. ... Chlorine I am still looking for a