CO2 Check - 20 mg per Litre

Our permanent CO2 checking solution “CO2 Check - 20 mg per Liter” can be used in every permanent CO2 testing device. It serves the purpose of controlling the CO2 levels over a longer period of time. An optimal level of CO2 is essential for the well-being of your waterplants and thus should be checked permanently. Our permanent CO2 checking solution has the advatage of testing the CO2 content independetly of the tank water so that no substances like e.g. humic acids can influence the test result.

Comes in a package with a volume of 250 ml.

There is too much CO2 in your tank. Please lower.
Optimal CO2 content (approx. 20 mg/l).
There is not enough CO2 in your tank. Raise slowly.


Fill 1 to 2 ml of our CO2 checking solution into your permanent checking device and put it into an area with good current in your tank. After 1 to 2 hours you can see how much CO2 there is in your tank. When the liquid is green, your aquarium has an optimal CO2 content of approximately 20 mg/l.

A permanent CO2 check is a very useful thing in a tank. Often the plants lack essential CO2 and do not grow at their optimum. A permanent CO2 check gives you a sufficiently exact reading how much CO2 you have in your water. The colourant bromothymol blue is used here as it changes its colour with certain pH values.

CO2 diffuses into the air bubble in the permanent test from the tank water and thus into the testing solution (and vice versa). Depending on its CO2 content, the pH value in the testing solution changes, and with it its colour. The constant carbonate hardness in the testing solution determines which CO2 concentration causes which pH value. The testing solution “CO2 Check 20 mg per Liter” turns a light green when its pH is around 6.6, which corresponds to a CO2 concentration of 20 mg/l. Thus you know that your tank water has a carbon dioxide concentration of 20 mg/l when the testing solution is a light green.