I'm trying to figure out how to do water changes with my Apex. The thing should have that capability without having to spend more on a separate system to do it. I looked at the Genesis systems and they seem to have a proven record, but the Apex is pretty powerful in it's own right and should be able to accomplish what should be a simple task.
The issue you have with doing it via the Apex let alone a pair of peristaltic pumps is that you typically would be using two seperate pumps which creates an issue. No two pumps pump exactly the same amount. The slightest variation in flow will impact salinity over the course of time. Then you factor in hose lengths which also impact flow. If the water in and water out lines are different in length and or different in height then the flow will change some more. If the pumps are at different heights, the flow varies. If the water level in the sump is lower than the water level in your salt water holding tank, then again the flow changes due to pressure from the inlet sides of the pumps. This is the case whether it's a conventional pump or a peristaltic pump.
The only way to get it close to perfect would be a dual head Cole Palmer pump and control its time intervals via the Apex. Problem there is that those pumps are extremely slow and noisy and if you want or need to do a faster large water change, you are more or less screwed.
I used to use a Litermeter 3 with a slave pump to change out 3.7 gallons a day. It worked great for that and I used it for nearly 3 years. My only gripes were that it is slow in doing so which wasn't a huge issue. The other gripe was the regular maintenance and calibration required to keep the pumps working consistently and at even flow rates. Then you also have to convert liters to gallons. It's also a bit of a pain to change the volume if you need to do a different size water change. If you need to do a large water change or a fast water change, forget about it.
I recently switched to the Genesis Renew system which in my opinion is one of the better upgrades I did to my tank. Prior to getting it, I designed I gallon metering reservoirs that I planned on using with my Apex. In the end, I decided that while I could save myself a bit of money by building my own reservoirs, the Genesis offered something that the Apex didn't. Simple flexibility to change out a specific volume every day or every week or if I wanted to swap out 40 gallons at once, push a couple buttons and watch it go. With the Apex, you would have create a bunch of programs based on time intervals, have float switches etc if you suddenly needed to do a 50%, 20% or what ever water change. The Genesis does it and does it perfectly every time without fiddling with programs.
A month or so ago I had a major disaster in my tank. That Genesis proved it's weight in gold. After rapidly changing out 200 gallons of water in 20 minutes via siphon and mixing pump, I used my Genesis to change out 50 gallons the next day followed by 40 gallons the following day and it was simple, brainless, reasonably fast and dead nuts accurate.
So in short, sure you can kludge together an auto water change system. The key is not having a situation that invokes drifts in salinity and that is something that is next to impossible to do with two separate pumps unless you meter exactly how much water goes in and out and the Genesis is the only system that does that and does it perfectly with no maintenance and no need for programming or calibration. Simply set the number of gallons you want to change and whether it's a one time big change, a weekly change or daily.
As for ATO, my Apex manages that and I have it set not to trigger the ATO unless the water level is low for more than 4 minutes which is plenty of time for the Genesis to swap a gallon.
I run a very large Apex system. I monitor salinity, PH, ORP, water on the floor, etc. I have 7 EB8's and over 40 active outlets along with 3 Tunzes and nearly a dozen flow profiles for them. I've got more lines of code in my programming than even I can comprehend and while it would have been very easy to create some programs for my Apex to do close to the same thing, it just would not have been as reliable let alone convenient.
I'm here to tell you that when it comes to doing water changes and doing them with pinpoint no nonsense accuracy, the Renew can't be beat. I could have done it easily with the Apex but it never would have been as good, accurate let alone efficient as a true dedicated device designed for just that purpose.
So there is my 2 cents. Take it for what it's worth. The Genesis is by no means cheap but for me, its worth every penny. That is if you can afford the space the metering bins take up. It's by no means a small system but boy does it work well.
