i run an extra filter on all of my tanks. works in my favor in more than one way. if i need a qt for a sick fish, i just pull the filter, set up the tank, its done. If im planning on buying new fish, ill set up the tank a couple days in advance so that its ready when i get home. Transferring water does nothing but transfer dirty water. the filter/media, decor, substrate houses the bacteria needed to "cycle" a tank. Also, a qt should be utilized for new additions as well, not just for emergencies