Hmmm... maybe I'nah, you dont have to test, but knowing pH tells alot. its probably the one test that i think tells more than others. pH helps with how fast corals grow, can be a cause for retraction, etc. it will also tell you if keeping a lid on it is as beneficial as keeping it off. the only benefit of having a lid on would be to slow evap, but evap is happening anyway, just at different rates. however, keeping a lid on will hinder gas exchange, which can change the pH of a tank. if things are going fine, it probably doesnt matter, and your attitude tells us that no amount of info anyone says, will change what youre doing anyway, so take it for what its worth.
testing pH at least once will give you a baseline to know if yrou coral growth is maximized or not, and will tell you if de-lid will benefit you, but that will make you go against everything that you dont want to do
And you trust it ? Serious question now. Lol. Just asking because I've heard the pH probes on the apex could get iffy sometimes. What should I test that with ? If I were to... loli have found that temp swings create other swings as well. i have found with raising and lowering of temps, salinity rises and drops, pH will also be effected a bit as well. i use an apex, so i can see a correlation through the day with the raising and lowering of water temp.