calcium reactor or kalk reactor..

With a Kalk reactor you shouldn't need to "mix" the solution. Just dump in a bunch of new into the reactor when it gets low - The solution should be saturated anyway so the excess floats to the bottom, gets stirred up periodically by a stirring mechanism to resaturate. I don't find that to be a problem.

 

The reactor will not be as effective and you are dosing impurities though. Impurities such as heavy metals precipitate out of solution quickly due to the high ph, as shown by Randy Holmes-Farley. This doesn't happen with a reactor, as it's constantly being stirred up. Also, it is tough to control the potency with a reactor, if you test the pH, it always ends up a bit high or low, not properly saturated IME.

I used one for many years, but went back to a simple bucket and couldn't be happier, just much more consistent. I test my alk every few weeks, it always reads about 9dkh.

For mixing though, I have a pre-measured measuring cup. I add 5 gallons of water to a 5 gallon bucket, take a quick scoup with the cup, add it in and mix for a few seconds, put the cover on, let site overnight, plug the pump back in, in the morning. Done... no dust or nose bleeds. Takes a minute maybe. The 5 gallons doesn't quite last week, but I just bought a 20g bucket, that should last 3 weeks or so. Kalk can sit for a long time as long as it is covered and not exposed to an influx of air.