First of all, the bigger the better. Most people that run QT tanks have them in the 10-20gal range. Basically you need 3 things.. a filter, light, and a heater. For the filter, anything will work you just need good water circulation, you could use a simple "waterfall type", to give your QT a type of mechanical filtration. Any light will work for all fish(you dont really have to have one, but its recommended to at least have some kind of light for your new arrivals). As with most tanks, you'll need a heater to keep the fish at the right temp. You dont need a substrate in a QT tank. Setting up a QT tank is just like setting up your main tank. If you have any more questions let me know.