Re: CO2 x Kh

[Dave Millman <dave at tactics_com>]

At 03:51 AM 4/1/2003, Gustavo Adolfo Lapido Loureiro wrote:

>Hi,
>I´m intending to add CO2 to my tank, which has the following measurements:
>Ph - 6.8
>Kh - 3.0.
>Considering those measurements, I think that adding CO2 at this moment would
>produce a sudden drop in Ph, which is not a good thing.
>So, I´m thinking in, first, raising Kh (by adding some sea shells to the
>external filter) to a level of, say 5 or 6 degrees, and then adding the CO2.
>
>Now, I raise some questions:
>1 - Is the above strategy correct?

According to the pH/CO2 charts, you currently have 14 ppm of CO2 in your 
tank. This means one of the following is true:

    * You are already adding CO2
    * Your tap water has a high CO2 level and you measured
       the pH just after a water change
   * You have non-carbonate buffers in your water. Have
       you added pH adjustment chemicals?
     * Your test kit is bad

In any case, 3 KH is just fine. You will not see a sudden drop in pH. KH 
declines slowly due to biological processes, but normal water changes will 
replace it. The only time you get a sudden drop is when KH is below 1 and 
drifts toward 0.