CO2 Measurement Revisited

Jay

I have wanted to post this update for a while, just to get everyone on the same page about testing for CO2 in a planted tank.

We should know that the pH/KH chart is not accurate if there are other buffers in the water such as PO4. Most aquarium water has quite a bit of "stuff" in it that can act as a buffer other than "carbonates" This makes the chart theoretically correct but practically useless.

The little chart in the Measuring CO2 sticky is more accurate than the pH/Kh chart but also has a few flaws (I'm not going to get technical here) pertaining to gassing off the CO2. It will get you trended in the right direction but is not spot on accurate. When you reach the point where CO2 is a vital part of your aquatic efforts then you need more accuracy.

Right now in the hobby the most accurate way to measure CO2 is with a little device called a "Drop Checker" Essentially a drop checker separates a sample of the tank water from a reagent reference solution by a small air gap. CO2 molecules migrate across the air gap (trust me it works) and change the color of the reagent solution. I realize this sounds very complicated, but in practical use they are very easy to work with.

There are some good ones and some poor ones out there.
I am experimenting with one made by "Cal Aqua" that eliminates the need to match a color card to the reagent change.

Jay