I just changed over my 10 gal. tank to a 55 gal. When I made the change, I put all of the gravel from the 10 gal. into the larger tank. I also have the filter from the 10 gal. running in the new tank. I didn't change any of the media in this filter. I've also added a new filter to the 55 gal. and my 7 fish are now living in the large tank. My question is, how long should I wait before adding new fish? My ammonia, nitrite, and nitrate readings have been at zero for three days (since I set the tank up.) I'm assuming that I successfully moved bacteria from the old tank to the new tank. How long should I wait to be sure that I'm not going to get any out of control ammonia and nitrite spikes?