pH question

Alright, so as pretty much everyone knows, pH is temperature dependant, and also, it changes during the day and at night depending on what state the corals are in. Currently, I see pH as low as 7.9 early morning (coolest temp, around 79, and right before the lights come on) and 8.2 in mid afternoon (warmest temp, around 81, and corals "active")
Now, most places I read say to keep the pH around 8.2, is that 8.2 at the highest, lowest, or average ? if the variation I get is 0.3, average would mean that my pH would have to get to 8.05 at the lowest and 8.35 at the highest ?

 

ph

Yeah at low side IMO would be 8.1 then high side 8.4

 

I guess I have to get a better pH indicator. I don't see the variation in pH that you are talking about.
Anyway, I would hazard a guess that the ideal is an average, about which you will have variation both high and low. So, 8.2 +/- 1

 

I am using a (calibrated) PinPoint pH monitor 24/7 on it, it's actually down to 7.85 right now yikes ! Tomorrow I will add some buffer (added some tonight, but it was actually the kind that raises alkalinity only since it was a little low at 7.5) so tomorrow I'll add the pH buffer and slowly over the next few days raise it so that the low is around 8.05 - 8.1

 

7.9 to 8.2 is actually not that uncommon of a ph range for reefs and lots of successful tanks are kept in this range. Don't worry too much.

I personally do not think buffers are necessary for reef aquariums. In fact they can lead to some major problems depending on exactly what you're using and how much and whether you're watching your alkalinity etc.

PH is mainly a factor of alkalinity (carbonate hardness) and dissolved co2 in your tank. If your room is well ventilated with fresh air and your alkalinity is good your ph should also be good if you are running an established reef.

This should explain a lot about low ph. Feel free to skim over any super-technical stuff, I think it's possible to get a good idea of how ph works in reef aquariums without digging into every detail.
Low pH: Causes and Cures by Randy Holmes-Farley - Reefkeeping.com