If they are small goldfish you may not see a spike at all as the filter will be able to build up the good bacteria slowly in harmony with the fish waste. If you are cycling slowly and properly this may be the case. I would do the once weekly water changes as you usually would, or when the nitrAtes get too high.
A tank is considered done when the ammonia and nitrIte have reduced to 0 and nitrAtes have begun to rise. The water changes will keep the nitrAtes low (aim for less than 50mg/l, less than 25 is better though)