I know that you truly believe this, but as you get more experience you will likely find out what so many other have... that using a co2 controller will only, at best, do what a well tuned system can do. At worst, using a pH controller can cause a lot of problems and inconsistent results. I have helped too many people that watched that dude's video where he tells you to throw the tuning instructions in the trash (he is out of the hobby BTS) that were fed up with their reactors and wanted to go back to 2/3 part - they are all happy now and truly know that consistency is.
If you want to use a pH probe to monitor, then cool, but I would not control anything with it.