yea, I have an apex that doses for me, I would like to have something to keep the saturation constant... inexpensively. I used a large mouth Mason Jar for my container...
OH NO..... I let it settle, I use Ro to push in one hose and the Kalk goes out the other into the tank, every so often I give it a shake to re-saturate the middle part. That's what I'm looking to "automate".
I'm building my own for my new tank. I just ordered a dosing container, some acrylic rods to make a stirring rod, and a rotisserie motor to mount on top. I plan on making a thread when it all gets delivered.
I've seen similar builds done. Seems like a pretty simple concept. It should work great in conjunction with your apex. My rodi feeds to a brute in my basement. From there water is pumped up to my top off reservoir. I was planning on using a float switch to keep water fed to the stirrer at the right level. I might go for an optical sensor instead due to the fear of the kalk causing the float to fail.