Time is hard to say, it depends on the tank, rockwork, filtration etc. In theory, there should be a point where the ammonia starts to drop, and then the nitrite goes up, then the nitrite should drop, and nitrate should go up.... in theory, at this point, the ammonia should be zero, which means it has "cycled". I haven't used this method in a long time, since its not really effective for the big systems I've had in the past. I used pure ammonia, did some complex math to find out how much to add to get 5 ppm then kept an eye on it till it dropped, added more, etc, basically to ensure that my system was ready to handle a heavier bioload right away (since adding inhabitants slowly increases risks of aggression).
