Using a drop checker kit is the most convenient and economical method to measure CO2 in your planted aquarium. It may be an essential part of any planted tank today because of its being effective and easy to use. In this article, I will cover how to use a drop checker as well as review the best drop checker kit easy to use for you.

Using a drop checker kit to measure CO2 in planted tank

A drop checker is a U shaped glass container filled with a indicator solution. The reservoir is build so that there is an opening that allows gas (CO2) exchange between the solution and your aquarium water. As the CO2 gasses off from the aquarium into the drop checker, the pH lowers and the color changes. By looking at the color in the reservoir, you can easily find how much CO2 there is in your aquarium.

A common complete drop checker kit looks like this:

Indicator CO2 glass drop checker test kitIndicator CO2 glass drop checker test kit

How to use a Drop Checker?

  • drop-checker-manual
  • Turn the drop checker upside down and fill it with several drops of CO2 indicator solution.
  • Tilt the checker slightly so the solution runs into the ball.
  • Turn the Drop Checker back over, and insert into the aquarium. At this point, the solution in the checker should be blue.
  • Waiting for up to 2 hours to see the color change of the CO2 indicator solution.

How do we read it?

Once the checker is in the aquarium, it will take a few hours before CO2 in the aquariums exchanges across the air gap. After 2-3 hours, CO2 in the checker and CO2 in the aquarium should be the same. The increased CO2 level in the Drop Checker will affect the pH which will change the color of the regent.

Change color of CO2 indicator solution

  • A healthy aquarium has a CO2 level of anywhere between 20 to 40 ppm. 30 ppm is an ideal level for both plants and fish.
  • A blue color indicates you have a CO2 level of 25 ppm (part per million) or less.
  • A green color indicates your have a CO2 level of 26-35 ppm. It is ideal if your checker changes to the green color.
  • A yellow color indicates you have a CO2 level of 36 ppm or more.

Normally, if you want to measure the CO2 concentration, you need to have an accurate measurement of pH and KH of the aquarium water then infer the CO2 level. However, with a drop checker, CO2 in the aquarium water is measured through the solution in the checker thus reduce the risk of error. So it is more convenient and economical than the method using test kits to measure pH and KH then infer the CO2 level.

Best drop checker kit for your fish tank

  • Best drop checker kitEditor's rating: Check on
  • Rhinox Glass Drop Checker Kit includes:
  • A glass drop checker to contain CO2 indicator solution,
  • A suction cup to bind the glass checker to your aquarium side,
  • A 10 ml CO2 indicator solution,
  • A 2 ml syringe,
  • And a color chart for reading the CO2 level.

For using the kit, only add 5 drops of CO2 indicator solution to the glass checker, then place them inside your aquarium using the suction cup. You should wait for at least 2 hours before reading the result.

  • Rhinox Glass Drop Checker KitRhinox Glass Drop Checker Kit
  • If the blue CO2 indicator turns green, congratulation, your aquarium has the right balance of CO2.
  • If the blue CO2 indicator still remain the blue or doesn’t get the wanted green, it mean the CO2 injected is insufficient and you only need to slightly adjust your CO2 regulator to get the right green.
  • If it turns yellow, your tank has excessive CO2 and you should decrease the CO2 injected. Once ensuring the CO2 injected is relevant, you need to empty the glass checker and repeat the test until you get the green color.

You only has to change the indicator solution if it turn yellow. When you use up your CO2 indicator solution bottle, you can buy a new one.

Rhinox drop checker replacement solutionRhinox drop checker replacement solution

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