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Re: [APD] Re: PH and CO2 questions



Unless I misread Paul Sears Article in TAG a few issues
ago, only about one part in 2000 of CO2 goes to carbonic
acid.

Scott H.
--- Andrew McLeod <thefish at theabyssalplain_freeserve.co.uk>
wrote:
> On Tue, 02 Dec 2003 21:31:55 -0700, Chuck Gadd
> <cgadd at cfxc_com> wrote:
> 
> > Clint Brearley wrote:
> >
> >> Tarah Nyberg wrote
> >>> However, In order to reduce the net amout of CO2 that
> you need for you
> >>> plants you can also reduce the KH. at a KH of 2-3,
> (36-50ppm) you will
> >>> need much less CO2 to keep your plants happy. I don't
> have the chart
> >>> handy, but this should be evident from the chart.
> >>
> >> What? This doesn't make sense to me. Why should the KH
> have any 
> >> influence
> >  > on how much CO2 the plants need? Lowering KH will
> just lower pH (if 
> > CO2
> >  > stays contstant) but have no effect on CO2 or the
> plants CO2 
> > requirements.
> >
> > You are exactly correct Clint.
> >
> > Regardless of what your KH is, you need to inject the
> same amount of
> > CO2.  Changing the KH only changes the pH at a given
> CO2 level.  And
> > we know that pH isn't what's important to the plants.
> 
> I didn't think the level of carbonates affected pH, which
> depends only on 
> H+ ions.
> Wouldn't decreasing the KH reduce the amount of carbonic
> acid absorbed 
> into hydrogen carbonates to form bicarbonates? Thereby
> increasing the 
> fraction of CO2 left dissolved as carbonic acid and so
> available to the 
> plants?
>

=====
S. Hieber

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