Attach the suction cup to the main unit and put five drops of reagent.
Turn the main unit to move the reagent to the ball and add 1.5 ml 4 dKH water or aquarium tank water into the main unit.
Mount the main unit to the tank approx. 5 cm below water level.
The reagent needs to be replaced once every 1 to 2 weeks according to the following procedure.
The colour of reagent in the ball changes according to the amount of CO2 dissolved in the water.
Compare the colour of reagent and the pH colour chart.