I added a Kalk reactor that I top off through. I have it configured through my Apex to only top off after the lights go off. This keeps the pH very stable. I had days where the tank pH varies by only .03 using this system. I have the power head on the reactor mix for 5 mins every 4 hours and the solution stays very saturated. Also only top off for 90 seconds out of every 10 minutes to flatten out the pH spikes and don't top off when th pH gets above 8.4 I can help with Apex programming if there is any interest.