Ok, you can go one way or both.. Let's start with the CR...
I would look into the GEO models because they are rock solid, made here and are pretty much set it and forget it units.. You will need a good cO2 regulator (Connects to the CO2 tank).. I recommend the reef fanatic, because it automatically sets the pressure, taking the need away from having to do that manually. Also, I would purchase a good ph controller and a CO2 tank.. The GEO models have a port for a ph probe directly in the main chamber. This probe will monitor the PH inside of your recator and cut the Co2 should the PH drop too low. You will also need a feed pump, like an mJ1200 unless you can feed the reactor off your return line.. Once you're all setup, you have to time the amount of C02 bubbles per minute (usually about 20/min, which is controlled by turning a small valve on the regualtor), which you will be able to see through a chamber in your CR (all reactors have this chamber). Now it's time to set your drip rate for your effluent( The water coming out of your reactor). This, as well as the bubble count will vary based on your tanks needs. I usually set my my ph controller so that the the PH inside the reactor does not drop below 7.3. You don't want your media to turn to mush by allowing the ph to drop too low inside the reactor (The larger ARM media is good stuff to use and has a slower more even dissolve rate vs. the crushed media). If the PH is too low in the reactor, it will probably have more of a downswing effect on your tank's ph, which you don't want. The nice thing about the controller, is that even if you have too much CO2 going into the reactor, it will stop the C02 flow once it hits your set point. So, the controller makes it pretty much bullet proof. Here's a good rule of thumb... If you can get your reactor to stay in the 7.3 to 7.5 range between the amount of C02 your dosing and the set drip rate of the efflluent, you're pretty much in good shape...
Now for kalk.. I happen to use both because my tank suffers from sub 8.0 ph without it.. So, I use it more for the ph control than anything else. My setup is very simple. I add kalk (2teaspoons a gallon) in to my 32 gallon RO vat.. I use an aqualifter pump connected to a reef fanatic Level controller to draw water out of the vat. I use and aqualifter because it draws water slowly and that's what you want when dosing kalk . You don't want to dose too quickly and spike you ph. saturated Kalk water has a ph of around 10.0, so that explains why you want to dose slowly. When the water in my sump drops from evaporation, the level controller kicks on the aqualifter and suck the water from the topoff vat into my sump. The safe guard, is the second float switch on the level controller. If for some reason the main switch sticks, the second switch will cut off the aqualifter and stop potential flooding or the addition of too much kalk to the tank (I would not auto dose kalk without a second float switch for a safeguard). I find that the best way to mix the kalk is with a strong pump that stays in the vat... Once the vat is just about empty, I fill it up with ro water, add the kalk. I cover the vat and let the pump run for two minutes.. Fresh Water will only absorb up to 2 teaspoons of kalk per gallon, so you dont have to worry about mixing too much. Allow the water in the vat to sit for four hours before dosing into the tank and make sure that you are not drawing the water off the very bottom of the vat to dose the tank. Draw the water fromat least 4 inches from the bottom for safety. You only have to mix it once per full vat. Whatever does not disolve will settle at the bottom of your vat and be there for your next mixing. Another great benefit of using Kalk, is that it binds phosphates in your tank, which is always a plus when it comes to contolling algae. Using it along with a calcium reactor offsets the downswing in PH caused by the reactor in additon to the the benefit above. I hope you find this information helpful. Good luck with your decision.
