a good summary of how to change water parameters.
http://www.chelonia.org/Articles/waterchemistry.htm

"Ways to increase gH
Adding limestone to the aquarium (this will also increase kH which in turn will
increase pH)
Adding calcium carbonate will raise gH and kH"

To lower the pH use hydrochloric acid, aka muriatic acid at your hardware store. Mix
the acid into water (not the other way around) to dilute and then use a gallon milk
jug with a bare pin prick of a hole to drip drop by drop into the pond. slowly
change the pH over a couple days.

HOWEVER, it could be with no calcium/magnesium ions your pH is fragile and will
change quickly sorta like distilled water will. I have quite soft water since it
comes out of Lake Michigan, just a bit of carbonate too. Need to put in organic
dolomitic limestone to bring up the hardness. However, limestone pavers can also be
set in the pond to moderate the pH. They will dissolve as needed. Ingrid

On Tue, 7 Jul 2009 07:28:45 EDT, Elizabeth wrote:
I still need to adjust general hardness,, currently 0ppm.. Luckily we
are expecting several inches of rain this week which will help with
alkalinity, currently 300ppm and pH currently 9.0.

Any good ideas how to raise GH when KH is so high?
Somewhere between zone 5 and 6 tucked along the shore of Lake Michigan
on the council grounds of the Fox, Mascouten, Potawatomi, and Winnebago