Well, if you want to use it for your main tank, be sure to sterilize very very well, and as TankGirl said, get all new media. But, I still dont reccommend it if you can avoid it. Chances are if you do this, (what TankGirl said) you probably will have no problem, obviously she doesnt, and I think she knows what shes talking about.. Its just not something Id personally do, but maybe I am just anal about those things. Maybe even fill the QT
tank with a bleach solution before breaking it down and running the filter in it would be a good idea as well, but never use the same media for the two tanks. Is there really a need for you to tear it down though... why not keep it up and running until you need it again.. because chances are you will at some point, and when that comes, it will already be cycled and such requiring little or no prep other than the meds you put in it. I think its always good to have the QT
prepared incase of a situation that will call for it. Just my opinion though, and Im not very smart, so never take my word for things!