G & K Meyer wrote:

1200 gal pond, rubber liner with stone.
Reason we checked was from response to question about plants.
I bought pool test strips that go from 6.8 to 8.4 ph and test last
night it was at least 8.4 ph so added 8oz of ph reducer, Checked this AM
still 8.4 so added 8oz more.
Fish seem to be doing ok. I read that best ph is 7.0 for fish?

A _stable_ pH is best for your fish. Which means a good buffer (like
limestone).
Any ideas on control of ph?

Absolutely no commercial "ph reducer", for a start.

What would cause this, besides concrete?
Could this be why some of our plants just don't look as good this
year?

Definitely. Your plants are more likely to be affected by high pH than your
fish.

We have never really tested water before. What is the best way to test
and how do you know when to test?

Try not to test for pH - it just causes headaches :-)

--
derek