Read there are PH controlled CO2 injectors? Who is that targeted for? If fishes can accommodate PH swing caused by CO2 can I ignore those controllers? I am afraid to pump too much.. I am just using 1 bubble per 2 sec. So far they are doing ok.. been two days of using this...
While fish can tolerate the pH swings caused by CO2, they cannot tolerate high concentrations of CO2.
Having a pH controller control a solenoid that turns on/off CO2 will allow you to control CO2 concentration via an indirect measurement (pH).
So for example, if you slowly increase your CO2 injection rate until you see your fish gasping for air, and find that your pH is (say) 6.4, then that would allow you to set your pH controller to a tad higher (say,) 6.5 or 6.6 without fear that CO2 concentrations would rise too high and suffocate your livestock.