Well, it's not just the current levels that will tell you whether the tank is cycled or not. What have the ammonia, nitrite and nitrate levels been doing? Ammonia should have first peaked. Then you should have seen a peak in your nitrites. As nitrites and ammonia levels fell, the nitrate levels should have risen to some steady level.
Is that what happened? If not, all sorts of other things could be going on. For example, although you do have fish that are producing ammonia, you don't have very many fish (and they're all small) for that large tank. So, one reason your ammonia levels might low is that you've never had much to begin with and haven't actually established the needed colonies of nitrifying bacteria!