You can put the dolomitic lime in your filter instead of the sock.

Oh that is a good idea! I never thought about adding it directly to
the filter. It won't clog it up?

but it seems it
has done the job of adding a buffer. Baking soda may increase the pH quickly (not
desirable), but it wont provide lasting stability cause the bicarb breaks down to CO2
and leaves the pond. That is where the dolomitic limestone comes in. It slowly
releases on demand as needed, almost like having limestone in the pond. anything
above 50 is OK, altho higher is better.

Oh, okay. Thanks. I added some more today, directly to the filter.

It is expected that pH is low in morning as the CO2 has been removed during the night
by plants in the water. During the day CO2 and O2 levels increase with pH peaking
right before sunset. But the more plants (algae) in the water, the larger the swing
... do you have green water? It could be if your water is green and warm then the
plants are using up the oxygen... especially if you dont have sufficient oxygenation.

Ah. Well, we have had an enormous amount of algae this year. It just
started to come under some degree of control within the last month.
The water itself isn't too green. But the algae have been clogging up
the pumps a lot. We do have a good-sized air bubbler in the pond.
It's about the size of a regular pump and it runs 24/7. Plus we have
a waterfall that runs most of the day. So I think there should be
plenty of oxygen, but who knows? Is there a way to find out? Should
I be adding hydrogen peroxide to the water??

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Thanks so much for your input.

Joan