I checked the ocean water by my pH sensor. It shows 8.5 pH. Unbelievable!
My water shows 8.7-88 pH. Two time unbelievable!

I calibrated the sensor. I used standart 7pH and 9 pH calibration liquids.
nothing changed

But the sensor shows 6.75pH for 7pH calibration liquid!!!
And 9.0 pH for 9pH calibration liquid

The chemical test shows 8.1pH for our ocean water and 8.3 pH for my water in the tank.

How to fix the bug of my pH sensor?