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Re: Alkalinity and Phosphates

James Purchase wrote (quoting yours truly):

> "The chances of getting interference from organic acids appears to be far
> higher than the chance of a problem arising from phosphate concentrations."

> Care to elaborate on that statement?

The main factor is that there is only a rather slim chances of getting 
phosphate levels high enough to change your alkalinity reading.  You would 
probably have to be trying.

I've followed up on two or three cases where alkalinity readings appear to 
produce erroneous CO2 concentrations and in each case organic acids appears 
to be the most likely cause of the problem.

Our aquariums should be organic soup.  Plants exhude organic compounds for a 
number of different reasons.  We daily add organics in the form of fish food, 
and plants are forever dropping leaves and roots are dying off.  The food and 
detritus are highly degradable organics.  Driftwood is a very large reservoir 
of semi-degradable organic material and soil or peat in the substrate adds 
even more.  All of the digestible and degradable organics can give rise to 
soluble compounds including acids.  Many of the additives we use -- e.g. 
chelated trace elements, "liquid CO2" and medications -- are organic 
compounds and some of those are organic acids.

Given so many opportunities I expect that quite a few aquariums will contain 
organic acids that might interfere with the alkalinity titration.  If the 
concentrations are high enough, then interference will happen.

Roger Miller