A pH meter will come in handy! And test the alkalinity of your tank water, not the alk of the reactor effluent.
Check your reactor often, the taps can quickly become blocked with deposits, causing a buildup of C02 inside the unit.
My second tip would be to get a fluidized reactor if you can afford it, their much more efficient with the media, and can almost use all of it up without getting blocked up.
My tip would be to forget about bubble counts and drip rates. The size of the bubbles and drip on each brand of reactor will be different. If you want to compare how your reactor is running compared to someone else’s you need to know the PH of the effluent and the rate of the effluent.
I set my reactor so that the effluent runs into a cup in my sump. I keep a PH probe in the cup 24/7. At a glance I can look at the PH of the effluent in the cup and how fast the effluent is running out of the cup into the sump and know that my reactor is working properly. When dialing in the reactor you can adjust it by changing the effluent rate up or down and adjusting the bubble count to keep the PH of the effluent at the level you want it. This also helps to off gas co2 as the effluent runs from the cup into your sump and will help keep the PH in your tank from dropping as much when you run a reactor.
I run my reactor at 6.7 PH after the 2nd chamber at an effluent rate of 400ml per minute. That’s for a 415 gallon tank with plenty of stony corals.
— Nathan Paden
I find the a flowmeter for the CO2 make adjust the PH of the effluent a snap
Like Nathan, I have the effluent run into a cup (actually, an empty container that 35MM films comes in is perfect) in the sump. I keep a PH probe in that cup.
I pump water to the reactor through a needle valve. This makes it easy to control the drip rate.
If you have problems maintaining magnesium levels as well then add pure dolomite to the reactor to help elevate Mg levels (happens pretty slow).
Dolomite is a mineral containing both calcium and magnesium carbonate, CaMg(CO3)2. As it dissolves it will add both calcium and magnesium.
The amount to add depends on the system demands and configuration of the reactor. It is not uncommon for 10% to 20% of the media used to be dolomite. Monitor and adjust as needed.
Get the dolomite from a reliable source and make sure it is pure.
— Richard Durso, “reefland”