What you want to do is get the tank running with new, dechlorinated water. Add your fish, then wait a day so that there is a little ammonia (just a trace!) for the bacteria you're about to introduce to eat. Then go to an established tank, take out a big mucky sponge and squeeze it out a few times in the new tank. The bacteria will instantly eat the ammonia and colonize your filtration. In about three days (often less) you won't see any ammonia or nitrItes. If you do, add more bacteria.
Remember that the sponge from the established tank may now be contaminated by your new fish, so you might want to think twice about putting it back in before cleaning it.