a pH of 7 is neutral so the Calc Reactor wouldn't work well if the pH is above 7. The water may not be acidic enough to dissolve the media. Have you tested the Ca in your water over time to see if the Ca is being replenished by the Reactor or is it being replenished by water changes? I run my reactor at 6.5 to 7.0 pH and maintain Ca at around 450 ppm.
I have been running my tank at around 7.9-8.3 for over a year and though not optimal, it's been pretty good. The drop in pH at night in normal and one option to negate that is to run a reverse light cycle refugium with some form of algae/plant to take up the CO2 and release O2 into the water at night.
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