Not sure about the NitrIte test, but I had the same problem w/nitrAtes. Both times I did a fishless cycle my nitrates would go through the roof and then drop to 5 the next day, usually in the last week or so of the cycle. In my case, nitrates would test low for 2 or 3 days and then go back up along with a mini nitrIte spike. So I always wait a week after the first time I get low nitrate readings just to be on the safe side, but I'm kind of paranoid, and since I haven't lost a fish yet I don't want to take a chance. I'm also using API tests.