Can you prime a drop checker for lower CO2 levels?

[snowballs99]

If drop checkers use a solution with a certain dkh to check CO2 levels,

Is there anyway I can create a solution to check for lower CO2 levels instead of 30ppm = green?

I want to experiment with substrates that generate CO2 and it might be interesting to use a drop checker to check CO2 levels from 10-20 ppm instead of the usual 15-30. (Assuming even hot organic soils would never generate enough CO2 to reach 30+ppm).

 

[Koan]

A drop checker is a poor tool for this:

How to measure CO2 levels in an aquarium

Too much CO2 or too little CO2 in your planted aquarium? How else to achieve optimal CO2 levels in your planted tank? Why drop checkers do not always do a good job. This page explores all these issues and more.

www.2hraquarist.com

For that level of detail, consider a CO2 test kit, Hanna has one

Carbon Dioxide Chemical Test Kit

The HI3818 is a chemical test kit for the determination of carbon dioxide by manual titration using a phenolphthalein indicator.

hannainst.com

 

[Art]

Fully agree with @Koan.

I guess an alternative is to use the drop checker but just see if you're getting any sort of color change. You wouldn't be able to pinpoint the 10-20 ppm though.

 

[Pepere]

My understanding is the standard indicator solution is made by mixing up water with 4 degrees of kh and then adding Ph indicator solution to it. As such it turns green at the desired co2 level.

I would guess that you could dial in the ppm co2 at which the indicator would turn green by using a different degree of kh water.


Perhaps though a better solution is a diy horizontal reactor built to limit co2 to deliver desired level and no more…

 

[Koan]

WFH day!

 

[Yugang]

Drop checkers use bromothymol blue, which is a pH indicator. The idea is that CO2 in the drop is in equilibrium with the CO2 in the tank, and that when we know KH we have a direct relationship between pH and CO2 in the drop.

As we can also see from the KH/pH/CO2 tables, at any given pH, KH is proportional to CO2 concentration. So when a 4 KH drop will produce lime green at say 30 ppm, then a 2 KH drop will produce same a 15 ppm CO2.




In summary, when you want to measure 15 ppm, start with distilled water, add some baking soda and calibrate at precisely 2 dKH , and some bromothymol blue. Lime green means 15 ppm CO2.