I can't speak for Cycling with fish as I have never done it before! But once your ammonia hits zero in and 8-12 hr. period, your Nitrite levels should be pretty high! And generally at this point you are a little over halfway done! When the Nitrites start to drop they will drop like a rock! I assume you are cycling with fish since you said the nitrites were dangerously high! Are you cycling the 30gal. in your sig with all those fish? If so it may take quite a while, That is ALOT of fish to cycle with!