Upon finding this site and registering, I have no idea why it is necessary to have a Quarintene Tank? Also when you buy new fish they must go in there for a week or however long.
The good thing about a quarintene tank is that your not introducing diseases to your pride and joy tank. You never know whats in the water from your LFS.
You never know if the new fish you have has a disease or something. It's the best way to keep most diseases out of your main tank. Everyone's happy, especially your fish.
basically waht everyone has said. A quaratine tank could be as small as a 10G or something, it's just as precaution really. It's recommended, but i dont' think everyone can really have an extra tank running just to be a quaratine tank..i know i don't
i'm probably walking on thin ice with an tragedy waiting to happne..but etiher i'm really good luck (which is unlikely) or my lfs just has good fish