[CleveYank]

When dialing in a Ca reactor.

You want to test the effluent for pH value to match your setting on your pH controller. (verify the value)
If 6.5 is your setting then it should test there.

At the same time you want to make sure that as you add or subtract CO2 bubble to your desired number to reach your target Ca and Alk level, that you are making sure that the pH of the tank is not being depressed by the CO2 bubble and the effluent output of the reactor. Keeping it no lower than 8.0 or higher than 8.6 with the 8.3 to 8.4 being the sweetspot so to speak.

******
Some folks in order to reach their target Ca and Alk levels have had to drip the effluent into their skimmer, into a refugium, or have a kalk reactor to blow of the CO2, have it absorbed by algae in the refugium, or use the high pH of Kalk drip offsetting the CO2 reaching the main tank. ----------I think the most common is having a dual chamber unit for this issue. Stage one is in your case gets a 6.5 pH and Stage 2 or the second chamber helps absorb the rest of the CO2 in the effluent so that pH depression in the tank is avoided. Every setup and flow and amount of Ca/Alk you need varies. So it's really pretty much a tailored thing. 30/min bubble rate for your 180 might be too little for the 180 tank of the next guy that has 12 inch diameter plate corals and 10 or 12 clams.

Using a B-ionic or 2 part to help get the tank at the levels you want and having the reactor maintain those is usually easier than walking the values up with the reactor.

The key to any of this especially if you have a wonderful SPS livestock now is to test and test and test and like anything else...slow adjustments.

Hope that helped clear up the bubbles...