CO2 - kH???

[TonyN]

Does injecting CO2 change the kH. My kH has been doing funny things the last few day. The only thing I added was some Seachem Clarity and started my DIY CO2 system right after that.
Now the kH has dropped about 30 ppm, so I dont know if it was the Clarity or the CO2.

[happychem]

No, CO2 does not affect KH. True it does react with water to form bicarbonate species, which contribute to KH, but for every bicarbonate formed, an equal amount of H+ is formed, which has the opposite effect on KH. In other words, the two balance out.

[resk]

Checked this product out online, I don't think it will affect your KH.

Perhaps it's something else..

What kind of KH test kit are you using, mine measures in dKH and not ppm.

Please post your current KH, PH, and CO2, and the test kits used to get the values

[TonyN]

Ok, I'm testing kH with a Lamotte test kit. For pH I have a Pinpoint pH moniter. Then I calculate the CO2 using Chucks calculator. Results as follows:

kH: 56 ppm or 3.1 dkH
pH: 6.79
CO2: 15 ppm

[happychem]

Next to pH tests, KH is the simplest one. All it is, is a strong acid titration. You add dropwise some acid to your water sample. The acid consumes the buffer. When the buffer runs out, the pH indicator (also in the bottle), changes colour to indicate the excess acid.

[djlen]

None of the above will change kH. You might want to raise it a bit to 3.5, but it should not fluctuate much off of the 3.1 that you are getting. A better test would be to let a glass of tap water sit on the counter for a few hours(to gas off) and then test for kH.
This would also be a good way to test your tap for pH, phosphates and nitrates as well.

Len

[TonyN]

Ok - thanks for both responses. This did happen on the same day I did a 50% water change, but I didn't even consider that.
I will check my tap water as you said. Maybe it was just a matter of the tank gassing out after the water change,

Thanks