In my original layout, I was going to use the drain water from an auto water changer too. However I know that having to monitor and adjust the salinity due to evap was something that I would slack on. So I scrapped that idea.
Here is my routine that have used to keep the tank stable for several months.
I have actually been using this QT tank set up for about 6 months and so far I have never lost an sps in it. average time in Qt is 4-6weeks.
Initial fill is with display tank water, and a large piece of live rubble. I manually top off the evap water every day or two, and this keeps the salinity stays dead stable. I just keep a bucket of fresh ro/di next to the tank, and once a day I dunk a cup in the bucket and top off, if I miss a day, its not that big of a deal.
About once per week or two I change out 50%(2.5gs) of the water, using display tank water.
I have a small HOB filter that I use to run carbon in when I feel it necessary, especially when first putting new frags in that may be putting off toxins due to stress.
At 4-6 weeks, once I have determined the frags are clean, I remove the frags, dip them one more time just to be sure (I have found nudi's after 6 weeks of no siteings), put them into the frag tank. The QT tank gets drained, cleaned, and refilled. I take the piece of live rock rubble out and throw into the dry rock rubble pile on the shelf, and replace it with another piece of live rock rubble from the sump. I have about 30-40lbs of rubble, so there is no chance of running out. Eventually the dry rubble will be cured again and put back into the sump. (may take a couple of years)
This is something in my system I've still not figured out!
