as long as you are using water from a CYCLED tank, you will not have to do any cycling on the
QT. right now you have a saltwater storage tank, not a
QT...
you should use that water for a water change when your cycle is done. (as long as it is simply aged saltwater) i would only fill the
QT when you are going to use it for a new fish... etc.
one very good option for your
QT is to store the actual foam / mesh filter media from you
QT filter in your main tank. that way, the bacteria will colonize your filter media, and you can simply place it in the
QT filter when you need to start QTing a fish. when you are done, clean the filter media very well and place it in the main tank again. you can also toss out the used media and put a new one in the main tank to seed with bacteria. never take the media directly from the
QT into the main tank... you run the risk of introducing things into the main tank that you dont want in there (i.e. paracites, diseases, copper, etc.)
~mike