Let it be until ammonia is not present, nitrites are not present, and nitrates are up. If in question can do small dose of ammonia and make sure the biological bacteria consume it and convert it to nitrate. Once that happens then a water change is due and cycle is compete. Of course, that's a very vague answer based on info given. If were to be able to post age, length of cycle, method of cycle, current pramenters, and any other vital system info could be more specific. I would not be the one to say what amount of ammonia to test your bacteria with however so I will leave that to the professionals. Hope this helps for now though.