I have a fresh water reservoir with a small powerhead in it, and the powerhead is connected to a double float switch (not valve) in the sump. When the water level in the sump is low, the float switch kicks the pump in the reservoir on (if that float switch malfunctions, there is another one about an inch above it as a back up -
www.autotopoff.com), and it pumps a low flow (adjustable) into my kalk reactor - output at the bottom of the reactor. The reactor fills and 'overflows' into the sump. There is a mj 400 in the reactor that comes on for 15 minutes 2-4 times a day. The current mj 400 has been in there over 6 months, and the previous one was there well over a year. Even without the mj400, kalk still gets mixed every time water flows into the reactor because the input to the reactor is at the bottom of the reactor.
The freshwater reservoir has a float valve in it connected to my DI system so it always stays full, unless I shut off that feed valve.
I like Paradox's system too, but I don't like the idea of having to balance the peristaltic pump against evaporation. Over the year, the evaporation in my systems varies a whole lot, and I didn't like having to constantly adjust the peristaltic pump in order to keep up with salinity fluctuations due to evaporation. The one thing that would make it difficult for me to sleep at night in Paradox's system is the float valve in the sump to complete the top off. In that environment, I would be too worried that something would foul the valve or make the valve malfunction leaving it either off or on. Also, going on vacation on Paradox's system gives the tank sitter something a couple extra things to pay attention to, and I would rather lessen the amount of stuff they have to think about.
I don't think one system is necessarily better than the other, they are just different with different maintenance requirements. Once a year I let the float switches sit in vinegar for a day instead of checking peristaltic tubing on a peristaltic pump.
There is always potential for disaster, in any system.
Back to bed!