pH balancing act help?

[Gestaltgal]

I'm having some problems with super high pH. My tap water initially reads at a pH of 7.2 with a KH of 19 (woah, right?). It's well water that goes through 2 house filters and a softener. 

After 24-48 hours, the pH reads and stabilizes at pH 8.3, which I think is WAY too high for fish and/or plants. Even when I mix in some parts reverse osmosis water (pH 7, KH 2), the tank water still gets up to pH 8.3. I have 5 small Pogostemon Stellatus Octopus and one small Anubias Golden.

Is this pH too high if I plan to be putting in guppies (I think so)?

Is this pH going to hurt my Neocaridina shrimp (blue velvets)?

I'll take any guidance I can get!

Edited February 24, 2021 by Gestaltgal

[Colu]

You could keep lake Tanganyika cichlid in pH of 8.3 rather than fighting your pH get fish that suit your local water conditions it is possible something else is effecting your pH have you put any rock in to your tank  that could be altering your ph

Edited February 25, 2021 by Colu

[Gestaltgal]

Update: introduced co2 to help the plants, and ta da!  pH is far more regulated (7.4 and holding). I think with such a high kh, the off-gassing is a problem. I'll be monitoring of the next week with regular checks before introducing any livestock!

[Eric R]

I think ph can fluctuate with CO2 as much as 1 ph level between when it's on and off, so it's worth checking it at multiple times throughout the day and night. 

[Eric R]

If you want to lower the kh or ph more, you can probably do so using more RO water. Also, are you using RO or RODI water?

[Gestaltgal]

I'm using RO. With well water, we have RO at the kitchen tap for drinking water. The co2 injection during the day with it off at night seems to be doing the trick, and I'm taking the pH 3x daily to get a feel for the fluctuations. As long as the pH doesn't fluctuate hugely, I'm hoping we found the trick.