Idea for CO2 meter using the Drop checker+ gas phase meter

Tom Barr

Staff member
Jan 23, 2005
I was thinking about using a CO2 gas meter to measure the CO2 gas content inside the inverted chamber like the drop checker, just larger. Place a gas analyzer probe in this, and read(you need to convert the Gas into liquid ppm- about 72:1 last I checked bubbling 1800ppm air + gas into water to get 25ppm dissolved, I could be wrong, but that seemed right back then).

This removes one boundary layer, and it can use IR method for CO2, which does not wear out etc and can easily be calibrated. Gas detectors are pretty common for CO2 and somewhat cheap.

Still, several hundred bucks:mad:

Since there's the conversion, the accuracy of 50ppm in the air is about less than 1 ppm in water.

At least this is how I think it might work.
You still have to equilibrate the air in the drop checker with that of the water.

There's also another neat, very accurate method I'm looking at.
See other thread with micro probes.

Tom Barr


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
Given the wide variation in CO2 concentration you measured with your CO2 probe, is there really a benefit to trying to measure CO2 concentration at any one spot in the tank? When that concentration can fluctuate a great deal with time, due to (??), that further reduces the value of a measurement made at one spot, unless a time averaged measurement is useful.

If only the fish were unaffected by CO2 we could just go entirely by how it affects plant growth. Maybe we need a "canary fish", one that gets a fluorescent red spot on it's head when the CO2 level is near maximum? Surely we have a DNA researcher among our group who can whip up a few samples of such fish for us to test.;)