Just for the monitoring and failsafe values yes. None of what you are monitoring with will notify you of anything. You have thousands invested in your tank and I'd bet that you would wonder how you lived without it once you had it setup. Your ranco could be plugged into the Apex EB8 and the Apex would serve as a secondary monitor for it. Your Ranco would continue to control the temps but if something failed, the Apex would intervene and shut it off while sending you a notification. Same goes with the CaRx although if you have that setup properly, there is almost no need to even have a controller shutting the Co2 off. My Ca Rx pH is so stable that that my Apex never shuts off the Co2. It only serves as a failsafe. This is in large part due to the use of a Masterflex feed pump that keeps a constant and precisde flowrate through the Rx and a great regulator that insures perfectly consistent bubble rate. If my sump level is ever too low (potential leak), my Ca Rx is shut off and of course if my pH is too low the regulator is shut off but neither of those ever happen.
Dosing can impact pH so if something ever goes wrong there, the Apex can shut off the doser and let you know of an issue. ORP is useful for trends and can notify you of a potential crash. Salinity monitoring is useful if you use an ATO. I use my Apex for ATO control and salinity monitoring is part of my many failsafes. Sump level monitoring beyond ATO is valuable as well. Sump Too High and Sump Too Low are important things to monitor. Especially if you use an ATO or AWC. Too High shuts the skimmer, AWC, and ATO off and sends a notification. Too Low shuts the AWC and Ca Rx feed pump, Co2 and Rx recirc pump off and sends a notification. I also use water on the floor monitoring and monitor multiple areas around the tank including the sump area, ajacent closet where some of my plumbing is and also my shed outside where my RODI and Mixing tanks as well as my Ca Rx are.
I control my Kessils, my Tunzes, my RD3 230 closed loop pump and all of them are in sycn with each other in terms of flow patterns. The Tunze's are used for surge flow and a number of other flow profiles including a flush cycle that kicks up detritus. When flush cycle kicks in, My RD3 230 kicks up to a high power to help kick up anything that may have settled and send it into my overflow. At night my Tunze's and closed loop all slow down and give the fish some relative calm while saving power. The Apex for pump control, even the Jebao's offers so much more control that it makes controllers like the jebao or even the Tunze controller look like a joke. It's really nice to mix things up during the day and calm things down at night.
If temps get out of line, I get a notification. I also have fans on my light rack that kick on and blow across the water should the temps get too high. My UV fliter is shut off should temps get too high. I push a button at my Mixing station and my mixing pump turns on for an hour. My skimmer neck cleaner turns on automaticly for 15 seconds once a day. If my return pump is off, my skimmer is turned off and doesn't turn back on until the sump level returns to normal so as to prevent the skimmer from overflowing.
Then there is feed cycles. Some people like to shut pumps off during feeding. Push a button and the pumps of your choice shut off or slow down. I have the Neptune Auto Feeder that I use for supplemental feeding and it's great. I can feed as much and as often as I want automatically or from anywhere in the world with the push fo a button my smart phone, iPad or laptop. I also use a Neptune Dos for a thawed frozen food feeder for additional supplemental feeding. That happens once a day but again, I can feed from the push of a button from anywhere.
I throw all this out there as it might give you some additional thoughts as to how you would use an Apex beyond what you are already conrolling from multiple interfaces. You could eventually consolidate those to the Apex or just use the Apex as the failsafe for those other devices. Either way, there is obviously a lot more that the Apex brings to the table beyond what you are already controlling seperately.
After about 5 years of using an Apex and more than 15 years of using my first Generation Neptune Aqua Controller Gen 1 before the Apex, I can tell you that I would NEVER run a large system without a great controller like the Apex. I couldn't fathom maintaining and monitoring my tank without it. Stuff happens and my Apex has always been there whether it was a reactor leak that occured while I was in Europe and saved me from a disaster or an issue with a dosing pump that I was using for my ATO and the Apex notified me of a high sump level. Power outage notifications etc. No way I'd run a big tank with the kind of money I have invested in it without the controller. The controller cost is peanuts compared to what we invest in our tanks between equipment and live stock but the peace of mind that the Apex brings is priceless.
