Swimming pool tester
With a swimming pool tester you can measure the chlorine content, pH-value and the alkalinity of the water. This way you’ll know exactly which chemicals you’ll need to add. There are various testers available.

How many and which chlorine tablets – maintenance products do I have to add to prevent green water ?

Measuring appliances to test pH-values and Chlorine levels so that (pre-emptive) green water can be prevented.