This isn't a sure thing plan and I'm not going to build it tomorrow. The thought is that I have a smaller tank (8 gallons or so) with a filter (with LR rubble), a heater, small PH w/ sponge and a big thing of cheato. The display tank and the new tank are connected via pumps (connected to a UPS).
When a fish is sick or I need QT tank, then I stop the pumps, remove the hoses and move the fish or add the fish to the QT.
When they are done, then we reattach the hoses and pumps, slowly mix the water over a couple of days, then move the fish back to the display tank.
Thoughts?