I personally would use already cycled water from an existing tank V/s new water,
It's less stressful on the fish, and they go right to the same conditioned water as they were use too.
As for your filter,
If you can't keep an extra filter running in your main tank for the occasion you need it.
Then simple steal a small amount of media from the already established tank,
(I keep extra floss in all my filters for just this type of thing, Gives me an instant cycle so long as you don't overstock the intended new tank.
Sometimes you can get whats called "a Mini cycle"
when transfering media from one filter to another to set a new tank up,
However Using already established water from your main cycled tank along with the extra filter media will lower the chances of a mini cycle from ever happening, ,
Personally Doing the filter media and stealing water from an already cycled tank I have always gotten instant cycles, The only time I ever got mini cycles is when I didn't use already cycled tank water from a pre existing tank.
Last edited by Chicklet; 11-12-2010 at 10:03 AM..