Backyard Aquaponics
A place to discuss aquaponics

Yep as Rupe says, patience is the key.

For a pond the high pH is great for them, the bacteria is happy with a high pH and the fish have gotten used to it.

Can you collect any rain water? If you can collect rain water and use it to top up your system or do small water changes, you will avoid all the excess carbonates in the tap water keeping the pH so high.

Right, adjusting pH should be painfully slow. Like shifting only about 0.2 per 24 hour period max if possible.

Anyway, if you can change over to using rain water to top up your system, after a time you will actually need to buffer your system back up a bit and provide some calcium, potassium, magnesium etc. And if you manage to get some veggies growing in a grow bed hooked to the pond, you will eventually be able to quit doing the water changes since the veggies should be using the excess nutrients.

Get a top up float valve or hose timer so mom or anyone else can't accidentally leave the hose running (this has happened to many people, it is not uncommon.) My systems get topped up via float valve from my rain water tank but you could as easily hook something like that up from an elevated water prep tank or rain barrel or rain storage IBC.

I don't like to use acid to adjust pH but if you have to do it, definitely do it in a separate prep tank. Find out the ingredients in the "acid buffer" since stuff from pond or aquarium shops probably contain something with sodium which isn't necessarily good for the plants.