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Re: CO2 vs. KH testing

> Date: Sat, 27 Oct 2001 16:51:09 -0700
> From: "Dave Berryman" <dberryman7479 at mediaone_net>

> Ok, first off a disclaimer.I am not a scientist or a chemist so my test
may
> be flawed.  With that said here is what I did layman style :o)

Your test kits also appear to have VERY poor resolution. To properly do the
experiments you are describing requires a pH test kit that can resolve to at
least 0.2 pH units (not the 0.5 indicated here) and a KH test kit that
resolves to 4 mg/l (about 0.25 dKH, not the 1 dKH indicated here. What you
are seeing is mostly errors in testing. And this led you to misinterpret
your results.

> Reason for test:
> I wanted to see if I could increase the PH levels by increasing the KH.

You can and you did.

> Also to see if I could lower the KH levels by lowering the PH by way of
CO2.

You can't and you didn't.

> After water change
> KH 2
> PH 7

KH is low, pH is low.

> 1 hour after adding 2 tspn baking soda
> KH 4
> PH 7

I would bet pH was really about 7.5 at this point.

> 2 hours after adding another 2 tspn baking soda
> KH 6
> PH 8

Increase KH -> increased pH

> 10-26-01 9:00 am
>
> Checked water in the morning
>
> KH 7
> PH 8

Increasing KH raises pH. The coarsesness of your test kits prevents you form
seeing a "direct" relationship.

>Thought the PH swing would be minor.  This is not minor to me.

With your test kits, you can't see a minor swing!

> KH 7
> PH 7.5
>
> I hour after doubling my bps CO2.  Started with 2 bps now up to 4 bps.
>
> KH 7
> PH 7 - 7.5
>
> 2.5 hours after doubling the bps CO2 to 4bps
>
> KH 7
> PH 7
>
> 4 hours after doubling the bps CO2 to 4bps
>
> KH 7
> PH 6.5 to 7

> 10-27-01 5:00 pm
>
> Just checked once more and found..
>
> KH 7
> PH almost a strong 6.5
>
> So I have now proved to myself that the KH is in no way directly affected
by
> the swing in PH when the CO2 is altered

Ta-daa!

> and that the PH is in no way
> directly affected by the swing in KH when the KH is altered.

No, you showed that adding KH increases pH in the first experiment. Your
test kits prevented you from seeing a "direct" effect.

> Which brings
> me to two more questions...how high is to high for the KH?

Select a KH to give you the desired pH with a reasonable CO2 level. A high
KH level does no harm, it just causes you to have a higher pH. Anything
greater than 3 and less than 10 is a reasonable range. 5 dKH, 15 mg/l CO2 ->
pH 7.0. A good range.

> And should I bring the GH up also?

A GH of 5 degrees is reasonable for most fish - leave it alone.

George Booth in Ft. Collins, CO (booth at frii dot com)
  The website for aquatic gardeners by aquatic gardeners
    Major updates in July '01! On-line book, articles and tech briefs
      http://www.frii.com/~booth/AquaticConcepts/