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Re: [APD] PH and CO2 Questions

Lowering your pH doesn't increase the CO2 content of the
water -- but the reverse is true: Increasing the CO2 in the
water lowers it's pH. Because KH raises pH and CO2 lowers
it, you can determine the level of CO2 by measuring KH and
pH. But incresing KH or lowering pH (by means other than
CO2) won't increase your CO2 level, only adding and
retaining CO2 will increase your CO2 level.

If you use other chems to lower you pH, then the CO2/KH/pH
table might not be accurate. It supposes that carbonates
and carbonic acid (from CO2 dissolved inthe water) are the
only significant players in setting the pH.

Best to add CO2 to get the level of CO2 you want for your
given KH. If that means the pH will be lower than you
desire, add KH buffer (such as baking soda) to raise the KH
and pH. But your KH seems fine.

Scott H.

--- rockel <rockel at attglobal_net> wrote:
> I am going to try the "Barr Method" and have all the
> nutrients in place. 
> Howerver, my CO2 (DIY) appears to be my limiting factor.
> GH = 110 mg/l
> KH =  70 mg/l
> PH = 7.4-7.5  (City water analysis - test kit also
> measures 7.4)
> Using PH and KH chart my CO2 is approx. 5ppm. From the
> charts I would 
> have to get a PH of 7.0 to get 12ppm.
> I have some PH Down by Aquarium Pharmaceuticals.
> 1. Is there any problems using this product?
> 2. If I  lower the PH to 7.0, (is this low enough), will
> it stay around 
> 7.0 until the next water change or will it vary up or
> down (other than 
> the morning and evening readings)?
> 3. With a 50% weekly water change using PH 7.4 tap water,
> will the 
> resulting tank PH be 7.2 requiring only a 0.2 PH
> adjustment to get back 
> to 7.0?

S. Hieber

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