Re: [APD] CO2 measurement

[Thomas Barr <tcbiii at yahoo_com>]

There's little issue with the CO2/pH/Kh table.

The problem is in the measurement of KH and/or pH.
Ph is fine if using a pH calibrated pen/probe etc and all the
electrical devices are off or well grounded.

Alkalinity test, the KH, measure only total alkalinity, not
specifically carbonate hardness. So hydroxide, borate alkalinity
and phosphate acids can play with CO2 determination as well as
user errors.

While seeking accuracy is useful in some cases, the reality of
the tools to determine the method are quite another matter.

It is not uncommon for careful aquarist to have 50-200ppm of CO2
and healthy fish, while some might have 30ppm reading and
gasping fish(generally due to low O2, but not always).

Accuracy to 5ppm +, - is about the best folks can realistically
hope for given the error of the best alklanity test kits sold,
is about 4ppm.

But.....even that assumes all the alk is bicarb, which is not
always the case.

Every method has a trade off and a set of assumptions.
Some better than others.


Rergards, 
Tom Barr

 

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