Too much bad experience with neptune products for me to let my apex handle it but to each his own. I am doing it the old-school way with a ph controller and old valves on the bottle. The ph controller takes all the guesswork out of it. Calibrate your ph probe, set the value (6.5) and you are done. It's only job is to turn on or off the CO2 and it keeps the ph a constant 6.5 in the reactor and it works perfectly. No need for a carbon doser with this setup because of the kamoer peristalic pump...and dont have to count drips or guess. I use the needle valve to adjust the bubble rate so the CO2 controller turns off less often but that is not necessary with the controller. I have a tiny feed pump that pushes water to the reactor and the kamoer pump to control the effluent to the tank. I tried it without the small feed pump and the Kamoer created a suction to pull the water in but it just did not work as well. It would suck air from time to time...probably that leaking PM reactor. This setup is by far the best tool to keep your alk stable. If you understand 2 part dosing then getting the effluent dosing dialed in was super easy with the kamoer pump since the ML/min is right on the screen.
I was using a PM calcium reactor but it sprung a leak and I got a Lifereef calcium reactor. Yeah, everyone says GEO is the best but they were about a 3 month wait when I got the Lifereef within a couple weeks. Hard to argue with a 10watt flow pump! Been on this setup for about 6 months and the media has gone down maybe an inch.