I do automatic water changes at a rate of about 25 gallons a week. I use a Litermeter 3 with a secondary pump module. One takes out water a little at a time and the other adds water from my salt water storage tank. While I am not familiar with the Genisis system, the litermeter allows you calibrate each pump for the enviornement. The hose length as well as height are variables that will effect the flow rate so calibration is one key element in insuring that you take out and add in the same volume of water or liquid.
You then determine the amount of liquid transfer per pump. After that, the litermeter will handle the water exchanges a little at a time over the course of 24 hours and continue to do so until you stop it. I have been using this system for nearly a year and my tank has never been happier. All I have to do is transfer RODI from my RODI tank to the salt water storage tank and add salt which I do on a weekly or b-weekely basis depending on my mood.
Its made maintaining my system much easier. Its probably one of the best additions I have ever made to my system.
As for why I chose the Litermeter... Besides the fact that I have never heard a bad thing about the product and only good things, Spectrapure has great support and is based in Az which is close enough to California that should I need anything, its only a day away. I also use a Spectrapure RODI and given the support I have received from them, it was a no brainer.
One other nice thing about the litermeter is that you can have a total of 4 pumps attached to the main unit which is nice if you also want to dose.