My pond pH is getting really high and I don't know why or what to do
about it.

Here are the vital statistics:
Water coming out of the tap pH 8.3
pH range during the day:
8.8 early this AM
9.3 late afternoon.
KH and GH around 150 ppm
NH3 and nitrite zero, thank goodness
Water temp around 60.

Currently using CaCl2 to keep GH up (water soft) and baking soda for
KH.

I know that pH values vary during the day due to photosynthesis. I've
removed all submerged plants, vacuumed bottom to get up fallen algae.
skim algae off top and manually remove excess string algae, and water
goes through UV light to remove soluble algae.

I recently did a water change of about 33%. What now? Do I keep
doing water changes? If, afterwards, I add baking soda back again to
keep KH up, will I be back where I started?

At what pH level do I have to remove fish due to danger?

Thanks.

________________
Joan G.Wikler
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