It doesn't have to be anything fancy! The size of the qt will be mainly based on the size of your incoming fish, larger fish = larger qt tank. It can be left as a bare bottom with maybe a piece of live rock or just use some large pvc pieces. I use a hang on filter and a heater and a power head in the tank for flow and is a 20 gallon tank, but some use tanks smaller. I also put a bag of seachem matrix in my sump for a week or so ahead for proper bacteria and either place in the tank or it also fits in my hang on filter. I just try to keep the fish with the least amount of stress as possible and also just use a cheap light nothing fancy or high power. Also you want to make sure and test this water and do water changes just as you would do to your display tank as long as the fish is in qt! Also if I am qt'ing a fish that sleeps in the sand bed I usually place a tupperware container of sand in the qt tank as well!