Are you planing to just keep the dem fry for the new tank? If so, keep the filter running on the tank you keep the fry in and when your ready transfer add the filter and fish to the new set up. Bacteria just sitting in water with no source of ammonia/nitrItes will soon die out. Even so, get a good test kit and keep your eyes on the water parameters and be ready to do water changes if you get any bad readings.