I have run a Kalk reactor, CA reactor, and dosing pumps, each for years at a time...... I loved my CA reactor, it was an amazing piece of hardware, and very easy to deal with when my system was young and had a limited calcium demand. However when the system matured and my clams became sizable and started to suck calcium. My effluent went from a slow drip to a heavy stream of 6.7 PH..... I basically lost my nerve, the reactor never let me down... I tried supplimenting with calcium chloride to lower the effluent but it became to much of a pain, so I switched to 2 part with dosing pumps..... I think it is cheaper and far less risky for my system. I would reccommend going with a Kalk and CA reactor at the same time like I did, it will help balance the PH, also go with a large reactor. There is nothing worse than having to break it down to add media once you finally get it calibrated correctly. Also invest in a secondary media chamber, and IMHO use mechanical valves to control flow in and out.... This was my experience and I never had a problem.