Re: NANFA-L-- hardness and pH

Bruce Stallsmith (
Mon, 29 Aug 2005 10:11:29 -0400

Strong photosynthesis will raise the pH of water by removing dissolved CO2
gas (not common anyway) and bicarbonate ions, the most common form of
CO2-derived compounds around neutral pH. Plant systems aren't as able to use
carbonate ions, CO3--, for photosynthesis so carbonate dominates the CO2
buffer system and raises pH. When I used to monitor a pond's pH with a
computerized system in the summer we found that pH could hit 10 on a hot
bright summer day, before returning to around 6.1-in-night as CO2 was able
to accumulate in the water again as photosynthetic demand decreased. And
this was in a pond considered to be sensitive to acidification.

pH is a secondary indicator of water quality processes rather than a primary
parameter. Total Dissolved Solids (TDS) and the various hardness measures
tell you much more about buffers and balances in a body of water.

--Bruce Stallsmith
along the Tennessee, waiting for Katrina
Huntsville, AL, US of A

>From: Laura Burbage <>
>Subject: Re: NANFA-L-- hardness and pH
>Date: Mon, 29 Aug 2005 06:23:08 -0700 (PDT)
>Thanks everyone for the advice. I'll give a little
>more info as to what I'm looking to do: In the
>established tanks, the water stays-in-high pH even
>with the fish load. Perhaps this is because I have a
>lot of plants (which are my main interest). The
>plants would like higher KH/GH than 2, so I want to
>raise it. BUT, if I raise it to where I want it, the
>pH goes even higher, to about 9! I do have plenty of
>fish in the tanks, and have soil underneath the gravel
>(yields CO2). I do not wish to do CO2 injection
>(PITA). So, how do I raise the KH/GH and keep the pH
>from skyrocketing? David - doesn't peat soften as
>well as lower pH?
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