Re: [APD] CO2 drop checker -- Or -- The gas is always greener in the other guy's tester

["Liz Wilhite" <satirica at gmail_com>]

Yep, exactly for what both of you have said.

People forget that there is (hopefully) a pseudo-equilibrium in the aquarium
involving hydrogen ions in various forms, CO2, CO3-- and HCO3-.  (Yeah, I
know people talk about H2CO3 but I'm still waiting for anyone to show me
proof it exists anywhere but in a chemistry book that cited a freshman book
written in 1952.)  Changing the pH shifts the equilibrium, no matter *what*
you use to change the pH.

I, personally, have problems with algae in my aquaria if my pH (measured
with a quality pH probe that has been calibrated) and KH indicate I have CO2
of 30 ppm.  However, if those numbers indicate 50ppm I usually have no algae
growth and good plant growth and health.

There are misconceptions about CO2 in the water affecting O2 in the water,
but I wonder at what concentration CO2 affects fish respiration due to the
inability of the fish to shed CO2.  Is it possible that the 50 and 90 ppm
CO2 concentrations I've calculated are correct, and that this actually
doesn't bother the fish i.e. they have no problem with respiration?  Or is
it that the KH test is measuring something besides carbonate and bicarbonate
so the number being used for KH is artificially high?  In particular, are
sulfate or other common ions detected by KH kits?  I guess I could test it
if I weren't so lazy, but I'd rather see a bunch of us just spin around in
circles trying to figure it out without real data.  ;)

Liz

On 10/17/06, S. Hieber <shieber at yahoo_com> wrote:
>
> Hmm, if there are other acids, they will reduce the KH by reacting with
> the carbonates and the pH/KH/CO2 table won't be affected at all.
>
> ----- Original Message ----
> From: Vaughn Hopkins <hoppycalif at yahoo_com>
> To: aquatic plants digest <aquatic-plants at actwin_com>
> Sent: Tuesday, October 17, 2006 12:22:38 PM
> Subject: Re: [APD] CO2 drop checker
>
>
> The problem is that measuring the pH and KH of the tank water doesn't
> tell you how much CO2 is in the tank water.  That water almost always
> contains some other sources of alkalinity and acidity besides CO2, so
> the equation relating pH/KH/CO2 isn't applicable.
>

-- 
Liz
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