To repeat what has been said: I don't think you really can, and I wouldn't want to full automate a reef tank.
What I try to do is focus on what can I do to save myself labor or make easier to do in my reefs.
Calcium/alkalinity- A calcium reactor is the way to go, IMO. Once you get it set up and dialed in, it is pretty much maintenance free except to visually check the flow and the CO2 left in the tank. Eliminates manual dosing for the most part. Maybe a minor calcium correction every 3 months for me.
mechanical filtration: I use filter socks, but not the felt type. These are the biggest royal PIA to clean and maintain. I use nylon mesh filter socks because they rinse off and are back in service in a couple minutes. Just blast them with a garden hose.
Water changes/mixing: My RODI is plumbed into my Water change barrel and my ATO reservoir thru a series of John Guest valves. My RODI runs off of irrigation valves, so all I have to do is prss a button on an irigation controller to fill my containers. I used a soldering iron to make a volume scale inside the brute WC container in 5 gallon increments, so you only fill to the level and it is right each time. As well, I turned off my pumps, let the tank water settle, and then siphoned off 5 gallons at a time, making a drain scale on the back left side of the tank glass, so now all I have to do is start a siphon and let the tank water level drain down to a mark and I am done.
I also have a dedicated pump in my WC barrel that mixes the saltwater and pumps it into my sump. I built a PVC manifold attached too the pump output with two ball valves, Close one and open the other, and the output mixes the salt and RODI, close it and open the other, and the manifold pumps thru 3/8" ID pex tubing permanently installed that comes out of the WC barrel and into my sump.
I do other things as well, but these are some of the major labor saving things I use in my system.
Dave
