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Re: buffering capacity

George Booth wrote

> > Date: Sun, 5 Jul 1998 23:43:34 EDT
> > From: RDotta7777 at aol_com
> >
> > It seems that the buffering capacity is the issue.  The water measures a
> > Carbonate hardness of 40ppm with the LeMotte test kit which I equated to a dCH
> > = 5.06.
> I don't think LaMotte makes a "carbonate hardness" test kit. Which test kit did
> you actually use?
> They make an alkalinity test kit with measures in CaCO3 equivalents. To get dKH
> from alkalinity (assuming bicarbonates are the only alkalinity producing ions in
> the water) divide ppm by 17.8.
> A dKH of 2.2 and a pH of 6.1 indicates a CO2 level of about 55 mg/L. I would
> suspect your CO2 would NOT be this high - that's a potentially lethal level.

I think you can see now why I thought the conditions you reported were
odd.  If your 40 ppm (=2.2 degrees GH) alkalinity is correct then your
CO2 concentration is very high even without supplementing it.  It would be
odd if that were true, and even odder if your tank could maintain such a
high CO2 level by itself.

Possibly, you have something other than bicarbonate in your water that is
contributing to your alkalinity, and the actual bicarbonate concentration
is even lower than is indicated by the measurement.  This would be
unusual, but if so then you will *really* need to increase the alkalinity
before using CO2.  Alternatively, there might be something wrong with the
installation of the pH meter (stray potentials or some such thing) that is
causing it to read erroneously low.

If your tap water pH is also this low you may have other problems.  Many
metals can exceed acceptable concentrations in low pH water.  Many cities
intentionally increase the pH of their water supply in order to avoid high
metal (mostly copper) concentrations.

Roger Miller