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Thread: CO2 Chart
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post #26 of (permalink) Old 08-31-2009, 02:57 PM
Left C
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Originally Posted by Cardinals View Post
Is it possible to have an planted tank pH 7 @ 6dKH without supplemental CO2 or non carbonate buffers (e.g. phosphates)? According to the chart CO2 would be ~18ppm, well above normal equilibrium values of 0-5ppm.
Originally Posted by Cardinals View Post
If I've looked at the chart right, pH 6.6 dKH 6.5 equals 49ppm CO2?
Doesn't a "drop checker" actually measure the pH (using bromothymol blue), not CO2. CO2 is then deduced from the chart according to your KH?
If your "drop checker" is green, using bromothymol blue, pH is ~6.6. Therefore, if your dKH is still 6.5 your CO2 is ~49ppm. However, if you have reduced your dKH to 4, then CO2 ~30ppm. (using the charts)
If you are interested, I am using excellent LaMotte CO2 titrator which could be used to verify your tanks parameters.
You most likely have other buffers present than carbonate/bicarbonate buffers in your aquarium since it is planted... Namely some phosphates which are much stronger buffers as you know.

"NOTE: If you aren't adding CO2 to your water, and the CO2 level based on the pH and KH indicates more than 5ppm, then it is very likely that some other buffer (such as phosphate) is present in your water. In an inhabited aquarium, the amount of CO2 produced by the fish will not have an effect on CO2 levels in the water. Any excess CO2 created by fish will dissipate into the air, leaving a fairly constant CO2 level of about 3-4ppm. If you test your pH and KH, and without adding any CO2, the chart says you've got 20ppm CO2, don't believe it. "

The above quote is from:

Most people don't rely on that chart anymore because of several variables including phosphate buffers, other acids and bases involved and inaccuracy of hobby grade test kits.

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