I am stepping outside of my area of expertise, but the manufacture of sodium
bicarb is by taking sodium hydroxide, (soda ash) and bubbling CO2 through it
so that the sodium + OH + CO2 yields NaHCO3. The concrete gives off calcium
hydroxide and the hydroxide, if pure has a pH of 14, though as calcium
hydroxide saturated it has a pH of around 12. I am guessing an excess of
hydroxide is causing the pH to be high, and by bubbling CO2 through the pond
the hydroxide would be changed to bicarbonates. Of course air stones would
bubble CO2 along with the other components of air. Underwater plants
produce CO2 at night, and in combination with air stones may help to lower
the pH.
--
RichToyBox

"Jim and Phyllis Hurley" wrote in message
...
I just checked the pond chem stats.

GH 75
KH 300
ph 9
Nitrates 0

Looks to me that the ph needs to come down and that that may be
contributing
to the problems of the WH.

How do we lower the ph effectively in a cement pond? It is in fact higher
than usual, generally, we have been in the 8 range.

Speak, O pond muses.



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