Yes you can if you just want to see what it is running. I have a PH controller with probe to monitor the PH in the effluent and control the amount of CO2 going through the reactor. I have it set for a PH of 6.5 using ARM media. I have a second PH monitor on the main tank as well. I have had to use a Kalk drip to keep the PH in the tank from dropping below 8.0.
I don't know about the pocket tester.