quarintine tank questions !

Most people just keep a spare 2ft tank as a hospital/quarantine. It may be left without substrate, but often at least a thin substrate will help keep fish more secure. An inexpensive filter setup is often the choice, I just use a simple sponge filter with a powerhead, but even an airstone will suffice. A heater is essential, as with many diseases a slight raise in temperature is part of the treatment. That is basically it. You can use a fishless cycle to start it, and seed your filter bacteria from your current tank. When the hospital tank is not in use, most people keep a few guppies or swordtails(any inexpensive fish) in the tank to keep it in cycle.
 
Agree with Kit.
Personally, I leave my Qtank (15gal) w/o fish or regard to keeping a bacteria bed alive in the filter.
You can just put sponge, floss, etc... from the q-tank filter (make sure it is clean!) in your display tank filter. This will keep bacteria alive on it until you need it.
-OR-
You can simply rely on water changes (which are usually daily in a q-tank since you are adding meds) to keep ammonia and nitrites in check. The problem with this method is when you're just observing fish to see if they are sick or not (like when you first bring them home from LFS) you have to do the water changes anyway. On the other hand, water changes on a small tank are not very time consuming.
 
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