Measuring level of CO2 in your planted tank

A Co2 Indicator is essentially a pH test. But instead of measuring pH of tank water. it measures the pH of your CO2 indicator liquid, which indicates CO2 levels. 

In any design of the Co2 glass indicator, there is an enclosed air chamber trapped between the tank water and the indicator liquid. The CO2 in your tank will flow freely into the trapped air, and then into the Co2 glass indicator compartment. 

As CO2 enters the air, it is absorbed into the indicator liquid. The absorption of CO2 is the result of the gas seeking a point of equilibrium, or equal distribution of CO2 in the solution and the air; the basic principle behind the function of the drop checker. As CO2 gas is absorbed into the indicator solution, it lowers the pH of the KH standard, which in turn changes the color of the indicator liquid. This condition of equilibrium allows the Co2 glass indicator, a simple glass reservoir, to provide a highly accurate measurement of carbon dioxide (CO2) in the planted aquarium.

Mixing up the Indicator liquids

To have an accurate reading with your glass indicator, you will have to add 1 parts of the concentrated Co2 indicator liquids to 4 parts 4DKH liquid. You can always pre-mix a big bottle for replenishing since the liquid will slowly get diffused/dissovled into the aquarium itself. Some brands offer pre-mixed liquid that saves you some time and cost.

What does the color change means?