Question about pH swings

[tomtom2245]

To start with, everything in my tank is growing and looking happy this is more of a curiosity question. I have found that my tank has pretty large pH swings: ~8.2 at night to ~8.7 during the day. I only run my skimmer during the night which has helped some. I don't have a sumo/fuge so running an opposite light schedule isn't possible for me. The only thing I can think of is I dose soda ash for Alk, at 50ml/day in my 20gal, it's pretty SPS heavy so it soaks up a lot. I could switch to a sodium bicarbonate or ash/bicarbonate mix if that would be better. The pH is measured with a probe and has been calibrated very recently. Any thoughts?

 

[tomtom2245]

My alk dosing is also spread out throughout the day over several small doses as well. I have a Bubble Magus and I believe it's set to dose over 24 separate intervals.

 

[saltyfilmfolks]

there's a few recent thread w randy. he seems to say 8.7 is hard to hit and not be dosing Kalk.
https://www.reef2reef.com/threads/ph-staying-high.280546/#post-3406937

 

[tomtom2245]

I'm going to try and recalibrate the probe. I don't think I accounted for temp differences. I'll let the calibration solution come to tank temp and the calibrate.