ph swings

I have a small ~8 gal water volume sps tank that i recently installed a controller on. I’ve been monitoring pH and noticed significant swings between day and night. I know swings are expect but the range is pretty significant - approximately 1 ph or more over the course of a day. I think it...

I wasn't aware the ph probe should be calibrated every 3 months. So it's been about a year and a half since I set up my tank and originally calibrated the probe. Yesterday I cleaned the prob and calibrated it 3 times and the readings im getting are not aligned at all with previous readings and...