I stopped trying to mess with mine. Too much time and too much money. My Ph is whatever comes out of the tap, 7.4 ish around here. I tried to lower it to "help" some fish once that liked lower Ph, ended up chasing it up/down and all over the place and lost a couple fish in the process. Forget that.
Unless your're buying exotic wild fish, the fish at your local petstore are probably living in the same crappy water that comes out of your tap, lol.
I don't think the OP is "messing" with pH for the fish. Rather, using a pH controller to turn CO2 injection on or off. Well, that's what I'm doing at least.
Basically, when you inject CO2, you bring down the pH. (Very few?) folks like me and the OP use a pH controller to keep injecting CO2 until the pH is dropped to the level where we think it corresponds to the appropriate CO2 levels in the tank. As a guideline, dropping pH by a full point means you have 30ppm of CO2 in the water (assuming that the water stabilizes at 3ppm CO2 without any CO2 injection). Using a pH controller set a certain pH, you are injecting CO2 up to a certain point, then the controller automatically stops injecting once that point is set -- that point is theoretically where the pH is dropped by the desired CO2 ppm. This is real-time and IMO better than relying on bubbles per second or a drop checker.
That is, of course, assuming that your tank water pH, outside of CO2 injection, isn't changing. I regularly have to put aside tank water in a bowl and let it sit to de-gas for 48 hours to check what my "baseline" is - this stems from my tap water being 7.6-7.8 earlier this year, and a little less than that this time of the year. Also important to note that the pH probe needs to be calibrated every 3-4 weeks, at least in my application.
On a side note, this pH drop is also often discussed here on whether or not it is harmful to fish and inverts. Some folks say it is ok, some folks say it isn't. So far my CRS indicate that it is ok, but I'm still waiting for them to breed before I can finally say with 100% confidence that it is fine.