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Re: Alkalinity and Phosphates
"Problems come up with the alkalinity (KH) test because the
method assumes that all of the alkalinity is bicarbonate.
When that isn't true -- as when there are organic acids
measured as part of the test -- then the assumption is
wrong and the test results are bad."
You've got to love it - it works when it works, but not when it doesn't.
Thanks to that article in TAG, I have a better idea of how much Phosphate
has to be present to interfere with KH, and the recent post by Greger
Lindstrand underlines just what can happen in a tank when that is the case.
B.T.W. Greger, were those 30-40 mg/L Phosphate readings completely natural
(i.e. from your tapwater)?
But Greger's example notwithstanding, from the number of books on water
chemistry which I have so far consulted, and the cursory reference to "other
sources of Alkalinity", I'd venture to guess that such contamination of
natural water, especially any water considered fit for human consumption,
has got to be very rare, and the water which comes out of most people's tap
follows the Alkalinity = KH rule far more often than when it doesn't. And
thus, its not something that most of us have to worry about. Am I making too
many assumptions here?
Roger mentioned an "organic soup" - (i.e. aquarium water) and I can see how
that might begin to show some of these influences. How practical would it be
to measure the Alkalinity of tapwater and compare that figure to the
Alkalinity of the water in the aquarium? Would the difference indicate