Midnight

Don't plumb it into your system, or it isn't a quarantine tank. Quarantine means isolated or stand-alone. You can move water from the display into it to get it started. It needs some type of filtration, like a biowheel or biopad. Don't add sand. If you put in LR, you are sacrificing it forever to the QT and will never move it back to your display.

With any QT, it is critical to top off daily to maintain stable salinity, and watch water temperature closely as well.

First posting YAY!!!!! Plumbing it in can have added benefits like added water volume, more live rock and sand to help with a large bio load and is a lot more stable than a 12 all my itself. But like Melev said its not a QT. Anything bad introduced into the nano cube is introduced into the DT. I have always liked the plumbed in dual tanks though, if you hide the plumbing well enough it looks like two separate tanks. I always have a lot of respect for nano/pico tanks the smaller the tank the harder it is to keep alive and thriving. turn your back on a 5.5g pico for a day and you are in some serious trouble. My 16 gallon cube is like a baby she needs love on a daily basis and can not be neglected no matter what is going on. I would have to say top off and temp are your two biggest issues. QT should be a simple setup though you dont need a lot of fancy equipment like a fuge or MH lights, A cheap biowheel and pc/t5 lighting will do the trick. But beware many people have tried to set in a QT tank and end up dropping plenty of coin in it making it a second tank.