Re: [APD] RE: Aquatic-Plants Digest, Vol 4, Issue 6

["S. Hieber" <shieber at yahoo_com>]

Yes, it's accurate enough.

Roger Miller did some math that he put on APD some time ago
-- It was quoted in one of the Aquatic Gardener issues in
the last year or so.  Basically, it takes a lost of
phosphate to siginificantly affect how well the KH/pH/CO2
table applies. He suspected that organic acids would
probably have bigger impacts. I think there is an even
bigger variable than organic acids, namely, the accuracy of
most pH kits. The color-match tests have a wide margin of
error. Throw in some inaccuracy for the KH test, too, and
the margin widens.

But I don't think this is a problem for aquatic gardening
purposes. A CO2 range from about 15 ppm up to about 30 ppm
works out very well. If you target around 20, the margin of
error still seems to keep one within range.

If one needs to fine tune, it will be because you can see
that some plants do better with more CO2 than you're giving
them and some do fine with less. Watch your plants and
patiently gain experience if you want to fine tune your CO2
levels.

It's a bit like using watts per gallon for measuring light
output. It's not precise but it's practical and generally
works or works well enough. And the alternatives (CO2 test
kits that become quickly inaccurate due to age or if you
shake the sample to much) can be much worse.

Scott H.

--- "Beek, Graham" <Graham_Beek at ds-s.com> wrote:
> If the C02 level doesn't change when changing the KH,
> then the KH only
> effects the pH. I'm understanding from this, that if you
> have water with a
> certain KH, it will always have the same pH (assuming no
> C02 injection). . . .From what I've read before other 
> factors
> influence the chart
> such as phosphates, tannic acids from bogwood etc. Is the
> chart that
> reliable in a real tank scenario?
> 


=====
S. Hieber

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