Doaner, your QT doesn't have to be a whole new setup like a display. A $9.00 10 gallon with a small air sponge filter is just fine. As far as cycling a new QT that isn't necissary at all. Some people keep the filter they use on the QT in the sump to keep a good population of bacteria on it. But say you were QTing a clown (not large and not a huge waste producer) jst check the ammonia levels daily in the QT as change water regularly. Every other day of 3 gallons should be just fine. Most people empty their QTs after each use. I do anyway. I use a small bio wheel filter and keep the wheel in my sump until i need it. If i ever have to medicate a QT tank I just buy a new one for the next time. No substrate in the QT, just a piece of PVC
for the fish to hide in.
The shimp doens't need to be QT'd as i believe they aren't subject to the same parasites as fish. I think you could do an easy 10 Gal
QT for less than $30 easily.
And QTing the first on is a good idea. You never want to medicate your main tank. EVER!!!!