From my last time I saw Ross's tank (long time ago) I don't rember him running a skimmer. Is this correct Ross?
Not having a skimmer, I suspect would make a huge diffrence.

Not having a skimmer would prevent the "blowing off" of CO2, which would help lower the pH, not raise it. Also, unless frequent water changes were done, accumulated wastes would increase the acids in the tank, again, lowering the pH.

skimmer
 

I actually do run a skimmer on my tank...but it is in my shop and not visible. I am going to pull out my probe and recailbrate it to make sure it has not just drifted a bit.