I spent about a year trying to go high tech (Journal) only to realize that the salt from my water softener was killing my plants. So I decided to take a page out of the book of saltwater tanks and built a water mixing/changing station. These stations are somewhat common for saltwater stations. Here is my setup:
Water from the RODI system enters the tank on the right. Waste water goes down the drain through the black tubing - the drain goes into my basement sump. Using the valves, I can use the pump in the middle to pump water from the RODI storage tank on the right to the tank-water tank on the left. That is where I remineralize my tank water. After I add minerals, I can set the valves so that the pump recirculates water in the tank-water tank to ensure that everything is mixed.
On water change days, I get a message on my phone asking if I want to prepare the station for a water change, four hours before I typically do a water change. If I say yes, my home automation system turns on the pump and a heater. I also have a temperature probe that allows me to monitor the progress of the heater.
I made this attachment for water changes:
I cut the PVC length so that it stops draining at about a 50% water change:
It connects to the mixing/changing station via braided hose with quick connects on either end. I set the valves so that the water drains into my sump.
To fill, I remove the siphon bulb, connect the PVC fitting directly to the braided hose, flip some valves, and turn the pump on to pump the remineralized water from my basement to the tank on the first floor. I can shut it off via my phone when the tank is full, but I have a valve on the fitting as a backup.
It was an interesting project and I learned a lot about PVC plumbing, which will be helpful if I ever setup a saltwater tank. Now I hope that the use of remineralized RODI water leads to success!