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measuring calcium and magnesium

I propose that we stop using units of hardness to refer to concentration
of magnesium and calcium. The appropriate units for those things are in
ppm or mg/L of Ca++ or Mg++. The usage of mg/L of CaCO3 is somewhat
useful because it allows one to use direct weights of the most commonly
used calcium salt however, test kits should give one and only one result
and that is the concentration of calcium ions (one test) and the
concentration of magnesium ions (another test). In the context of the
nutrient requirements of plants, those are the ONLY values which we need
to concern ourselves with. 

In the context of the alkaline mineral requirements of fish, I submit
that discussing mineral hardness is also inappropriate. Folks tend to
think of needing to attain soft water; IMHO you shouldn't be concerned
about the need for "soft" water except when you need to stimulate
breeding behaviour. In that situation, you simply need to use colder and
purer water than what the fish are currently acclimated to. IMHO.

For measuring alkalinity, I propose that we should use units of
equivalent CO3-- however there may be a more precise scientific measure.
The units of KH, while common, are nearly as _abhorrent_ as the other
measures of hardness. We are really talking about pH and the ability to
buffer pH changes. Alkalinity is also relevant to the discussion of CO2
concentrations and this is where we are interested in the
carbonate/bicarbonate ion concentration.

The issue is NOT:

"are we analytically-enlightened individuals able to apply conversion

The issue IS:

"what units should test kits use?"   and secondarily

"what units are relevant for discussion of plant nutrient requirements
and CO2?"

Steve P

PS My sincere apologies for mentioning the dreaded H-word again. ;-)