Baking soda is your answer. It is a buffer which would result in a pH of
about 8 when added in sufficient amount to overcome the acid. And, it's
cheap. I have a 2000 gallon pond to which I add a pound of baking soda from
time to time as needed. Calcium carbonate can be kept in a mesh bag to
slowly dissolve and add hardness and some buffer capacity too but not as a
remedy fix it.

--
Jim and Sara Humphries, Victoria, BC
"Tony Rivas" wrote in message
. net...
Greetings all,
I have a 2200 gal backyard pond with about 20 2-3 inch comets and koi and
about 1/5 plant cover. This week my pH is at 6.5
How can i get it up to a good range. Can anyone recommend a good amount of
baking soda or lawn lime dust to put in the pond to fix it. Could the pH
have gone down due to a berry tree dropping berries in it all month?

Thanks to all,
joe