rising ph, how to resolve?

[Douglas]

My ph phrobe is reading 8.53 in the am, and goes up to 8.8 in the late evening. Seems a bit high. How can i resolve this issue of a high ph? Or is it a concern?
HK 7.5
Cal 400
mag 1250
Sal 1.025

[reefmandan]

How are your corals looking? Polyp extension can be quite indicative of water conditions. Typically with pH being too high, it's a measurement problem, more likely than a parameter problem. Can you calibrate your pH probe?

[Douglas]

It has been a year or more since I have cleaned, or recalibrated the probe, I'll try that this week, and see if this will help. My coral extensions look ok. I'm using a different salt right now, due to stock availability.

[xenon]

I would bet the probe is off and requires recalibration.

[Myka]

I'm voting for the probe too. You really should be cleaning and calibrating it once every month or two.