Calcium Reactors sound big and scary.. however they can actually be quiet simple once you understand how they work.  At its core you just injecting Co2 into a chamber full of coral skeleton to slowly dissolve it.. then dripping this nutrient rich water (called the effluent) back into the tank.

To tune the calcium reactor you have two adjustment,  The drip rate of the effulent into your tank as well as the bubble count of how much co2 your injecting.    You want to keep the PH inside the reactor at 6.5-6.7 to dissolve the media but not too fast.. if your PH was to drop too low you would melt all of your media and turn it into mush.

To make setting up a CO2 reactor easier i highly recommend using a PH controller as it will make your life much easier and act as a fail safe. When the PH hits 6.5 it will turn off the Co2, the PH inside the reactor will slowly rise and when it hits 6.7 it will turn the Co2 back on.

Having a PH monitor lets you see how your bubble count is affecting the PH inside the reactor. It may take some time but once you find the perfect bubble count your PH inside of the co2 reactor will stay consistent and the co2 solenoid will stay on and just be used as a backup.

I apologize for the cellphone video but here is a quick video i did for a form post a while back