Welcome to R2R! Stability isn't really a tank cycler as much as a bactieria helper. That may be why you aren't seeing ammonia get to high. Get yourself a raw piece of shrimp, uncooked, and place it in the tank. Once you see it skim over, trust me you will know, pull it out with a net. Test ammonia and watch your levels.
Good looking tank....gravity defying even! lol