I use a Geo's reactor. Smith gauges, Milwaukee ph controller and the 957 solenoid set up. It is "not" hooked to my apex. Was great on my 125g. Now its working on my 500g. In the beginning you need to test Alk and Cal a lot. Once you have it dialed in you just look at the ph of the probe to be sure it has not moved, media in reactor (to be sure its not empty) and drip rate of the affluent. No more mixing / dosing mess. This time I added some neo-mag to the reactor, so I dont have to dose mag.
Just my opinion