VERY HIGH PH

[Yanir34]

Hello my SPS dominant tank is running for 9 months .
I calibrated ph sensor of my GHL profilux 4 1 month ago , and since then it show readings of 8.75 ph at day and 8.50 at night .
before the calibration, it showed 8.4 at day and 8.2 at night.
Today I calibrated it again with 7.0 and 10.0 Pinpoint ph calibration solutions, and still It showing high readings.
corals and fish are o.k , but I'm worried that it's not good thing for them .
Only change that I done was to cut off my refugium, and start dosing 50% recommend dosage of Bacto Balance.

Parameters:
Alk 7.8
Cal 430
Mag 1310
no3 at 4
po4 at 0.02
Salinity 1026
tepmeture at 24.5

What can cause thus readings, and how can I fix it ?

 

[David_CO]

if you're not dosing a massive amount of kalk or another extremly high alk additive your readings are false and you may need to get a new PH probe.

I dose alot of kalk and my PH never goes above 8.55 when I leave town for work and my indoor CO2 bottoms out.

 

[Yanir34]

if you're not dosing a massive amount of kalk or another extremly high alk additive your readings are false and you may need to get a new PH probe.

I dose alot of kalk and my PH never goes above 8.55 when I leave town for work and my indoor CO2 bottoms out.

I don't dose KALK.
I'm dosing Red Sea balling method (Liquid alk, cal and mag)

 

[Randy Holmes-Farley]

I agree the measurements are in error in fine fashion. High pH does not happen in the absence of very high pH additives unless it has almost no aeration.