The Dennerle Crabo Test Precision is a long term test for continuous and direct CO2 measurement in the aquarium. The Dennerle long-term tests are available in three different sizes and are made of high-quality crystal glass. The white inner tube allows the colour of the indicator liquid to be seen at a glance, regardless of the background. The compact, spherical design ensures that the test reacts quickly and reliably to CO2 fluctuations in the aquarium. This is how Carbo Test Precision works: CO2 diffuses from the aquarium water into the test vessel and dissolves in the indicator liquid. Depending on the CO2 level, the indicator reacts with a colour change:Blue = too little CO2Green = optimal CO2Yellow = too much CO2 Using the detailed stick-on colour comparison card, you can accurately determine the CO2 content in g/L As long as there are no other substances in the water that influence the pH value (e.g. humic acids, nitrate, pH minus preparations), you can also measure the pH val