Thanks for reading my question.

I'm using a co2 scrubber on my skimmer.
Most of the time my pH stays well in acceptable ranges, but if I open my windows my pH get to high due to overscrubbing.
I'm talking 8.7+

Now, if I want to program my p4 to shut of my skimmer if pH is rising above 8.6, how do i do that?
I'm not sure how to use the programmable logic for this.

My skimmer is on my 3th socket at my PowerBar.

Thanks in advance