I would go with the 30g. A Qt consists of the most bare bones system you can afford. Or just short of another display. People do both. I would say bare bottom, no rock or sand. and a few pieces of pvc for hiding. heater,something to break the water surface, and a filter, preferably one that has biological and mechanical capabilities. A bio wheel is good, or the standard most people have done is a sponge filter with an airstone. You would do well to seed a sponge in your fuge for a while to get some of the bacteria. With it being a completely seperate system away from your display, it's going to start fresh of bacteria. It's also sound practice to fill it with some display water, Though it will take a third of your system to do it. You can fill it with what you would normally do with a water change. It may seed it some with bacteria, but it's best with a sponge. I recommend Hypo salinity for treatment as it doesn't have any ill effects on the fish, and just as effective as copper. What I do is a day or so after all of the fish are acclimated into the QT, start dropping salinity by water changes, but instead of pouring back same salinity water, replace with fresh water. Continue this until the salinity is exactly 1.009-1.010sg any higher it's less effective. Any lower and it could damage the fish in the long run. After it is 1.009-1.010 (it really needs to be done with a refractometer or lab grade floating hydrometer. The swing arm is always off) after you are there make a water line at the water level. Than, top off evaporation.
6-8 weeks and you are right as rain! Water changes are done replacing with premixed water at hypo.
Important note* after the treatment take a week to bring it back up to display tank level. don't go over 2 ppt a day. It can send the fish into osmotic shock. I did this and got lucky I didn't kill any fish.
