# CO2 online calculator



## Emily6 (Feb 14, 2006)

Hey so I called my LFS to see if they had a CO2 test kit available (didn't want to waste a trip) and she said they didn't but there's calculators online that determine the CO2 in your tank based on pH and KH. Here's the link to the one I used:

http://www.fishfriend.com/aquarium_co2_calculator.html

Anyway, this seems too easy- are these accurate?


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## Bert H (Mar 2, 2004)

There is relationship between kh/pH and CO2 levels, but this relationship can be skewed by different factors. It assumes that bicarbonates are the only buffering sources for your tank, and of course, that your pH and KH readings are accurate. It's a decent estimate. Another estimate is to take a pH measurement of your tank's water when CO2 is flowing freely. Then let the water degas (sit out at room conditions overnight), and measure the pH again. Typically there will be a change of approx 1.0 pH unit from the gassed vs the degassed version of pH. The degassed will be higher.

The best measure we currently have is the drop checker. Very easy to use, and accurate.


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## Emily6 (Feb 14, 2006)

Thanks for the info- I'm a little uncertain of the results I got using their formula- it says I have 28-33ppm of CO2. My indicator is blue, making me think I don't in fact have quite that much. I'll probably buy a drop checker but I needed something ASAP at the time. Now that the crisis has past, I can think about it again.


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