Don't mess with the Ph too much. According with the experts messing up with the Ph is the major reason for discomfort and stress to fishes. Do you have a concret pond or with buthyl liner. Sometimes concret or untreated cement may increase your Ph.
A bag of peat may reduce your Ph and also acts as a buffer, all the chemicals are useless the water usually bounce back to the initial Ph.
Dont forget that during hot afternoons plants tend to increase the water's Ph and is nothing one can do about it.
7 Ph is (allegedly) ideal, anything between 6.5 and 8.5 is good.
9 Ph is not that bad, the worse thing is a Ph that fluctuates.
My water water was testing ideal from all points of view just the Ph was 8.5. In my stupid ambition to bring it to ideal (or close) I messed up with the Ph using different chemicals and solution such as Ph down...etc. Result? The water always has bounced back to 8.5, even worse I lost 9 fishes that had suddenly developed velvet and fungus. I put a 2Kg bag of peat inside my 500 gallons pond and the water ph has slighlty gone down to about 7.8 and stayed there for the last 3 months without any loss of fish.