pH cycle...too high?

[untamed]

Now that I've begun to monitor the pH, I can see that the tank is reaching a daily high of over 8.8. That seems unusually high to me.

I've just recalibrated the sensor, so I believe the readings are accurate.

I'm running my Ca reactor at only a pH of 6.8. I'm not dosing Kalk.

Do you think this is something that warrants some kind of correction?

I still have a lot of algae growth. Could it be that I just getting a large amount of photosynthesis taking place that is driving the pH up?