Much more important than the pH is the KH carbonate hardness. If it is not
above 100, then the filter bacteria will suffer and the pH can come crashing
down, being very unstable. You can raise the KH with baking soda and it
will tend to bring the pH closer to 8.4. That high of a pH may not be well
buffered.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Kevin" wrote in message
m...
Wow! Establishing a new 5,000 gallon pond, doing some analysis on the
water and my electronic pH meter shows the tap water in my town at
9.4. Shocked and disbelieving I checked the water company's website
and they claim a pH of 9. Isn't this pretty high? If I remember my
high school chemistry isn't water supposed to be around 7 to 7.5?
Axelrod's book suggests an ideal range for Koi of between 6.5 and 8.0.
How the heck am I going to achieve that?

My new pond has an automatic fill/overflow device on it. This will be
supplying a very small amount of makeup water at a pH of 9.0 it seems.