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Re: KH-pH-CO2 tables



Date: Sat, 15 Dec 2001 09:10:39 -0700
From: "Roger S. Miller" <rgrmill at rt66_com>
Subject: Re: KH-pH-CO2 tables

> Doug's tank seems to have a pretty extreme case.

As I do ...

> In the course of those tests we also found that the two-pH test that I
> have touted as approximate but interference-free is subject to
> interference from an acid that associates between the two measured pH
> values.

As worried about the fact that the tank is at 25 C and my room (so the bucket ) at 18 C...

 
> IMHE, the table's a good tool to get people to think about measuring CO2,
> but it doesn't provide a useful function except as a kind of teaching tool.
> This should of course be read as a call for testimonials of the fantastic
> value of the table!


> My reasoning is that the low tank pH favors fungal activity.  The fungus
> may not be evident either because it is growing mostly inside the wood
> or because it's removed from the outside of the wood by rasping or
> surface-grazing animals.  At least some varieties of fungus that
> decompose wood in purely terrestrial settings produce acids in fairly
> large quantities.  Perhaps the same thing happens under water. Low pH
> leads to predominantly fungal decomposition of the wood, the fungal
> decomposition produces weak, low equivalent weight acids and the acids
> build up to a sufficient concentration to effect the KH titration. 

No trace of fungi...
But soil to anaerobic in my opinion i.e. plants with established roots are OK.
Other (bulbs/rhizomes ones) have difficulties to produce roots before rotting...
Trying now to put P. Gayi everywhere to make my soil better !

> Thus, the KH-pH-CO2 table is not valid.

I think so...

pH 5.8 to 6.1
KH 7

Letting my pHmeter 5 min. for temperature compensation I read 6.1
Then shaking it I go down to 5.8 back quite soon to 5.9 then 6.0, later to 6.1 !


> Peat can also produce acids that invalidate the table.

Surely I use peat in my Eheim filter (8 tsp. from 32 changed every month).


> If true, then the combination of low pH and wood in the tank may be a
> condition in which the KH-pH-CO2 relationship is consistently
> undependable.  I'd like to hear some additional experience either way.

Lot of wood too in the tank...
Also PO4 rated greater than 20 PPM by two test kits although I change water (15 % per week)
and I stopped using pH buffering one year ago...  Only powder food...
Tap water KH at 4 !  No PO4...

> Roger Miller

Philippe