Your setup is very similar to what I plan to do. The only thing I have been contemplating is how to ensure there is no contamination that gets from the QT back to the display. My first thought is to not let the fill line on the QT touch the water, but what if I accidentally splash it or something. Maybe it's a slim chance, but since I am also an engineer I am always looking at failure modes.The water seems to clear up after a couple hours but the reading takes much longer. I know it does not matter but I am an engineer so these things intrigue me.
I test salinity every weekend with my hydrometer just to make sure everything it correct. I have been very happy with the auto water change system. I am changing 1.4 gallons per day spread out throughout the day. I started on July 19 and since then my salinity has ranged from 1.0256 - 1.0263. I plan on adding a third pump this weekend to start running that thru the coral QT tank.
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