get some muriatic acid, hydrochloric or HCl from the hardware store.

[snipped for bandwidth]

Okay, thanks. I had thought that might be a good thing, but I was a
little afraid.

a combo like dolomitic limestone should
work, but did you actually get dolomitic or did you get "slaked lime" which is CaO
and dissolves fast and makes the pH swing high.

It was really dolomitic limestone. A real PIA because I made the
mistake of choosing an agricultural mix (this was last spring) which
filled my pond with *mud* and took me all season to get rid of. Major
cleanup on the bottom, too.

the other problem is "plaster of
paris pills" which seems to do the same thing, swing pH around.

Oh. I'm glad to know that. I had heard that that was a good thing to
use. Glad I stayed away.

what kind of aeration do you have?

Good-sized waterfall.

Joan