LFS said that in a 120g the salinity changes so infrequently and a properly calibrated refractometer is so quick and easy to use that the money is better spent on an ATO or something else. For ATO, I think I will be plumbing in a RO/DI (it should be a very simple 1 hour project) in my basement and running it into a "T" valve. One side of the T will go to a 32g collection vessel to mix salt water for water changes and the other side will run upstairs to the sump attached to a float valve. I already have the RO/DI unit so the cost of doing it this way, in my opinion, trumps buying an ATO.
The wife is going to kill me...
Because float switches have a bad habit of accumulating salt creep, snails, crabs.........., and thus have a much greater tendency to fail as opposed to the electronic optic eye that the Tunze uses. Plus the other safety features like a second switch to shut off the pump at a pre determined high water mark in the sump, and a shut off of the pump should it run longer than 10 minutes.
You can do all that with any ATO connected to the Apex. I can do that with my Tunze, or my jobs as long as it is plugged into my EB8. No break out box needed.
