My tank is a 30 gallon and has three zebra danios to assist me in my fish in cycle. Yesterday I did a water change of 25%. Today, it had 0 ammonia, 10-15 nitrates, 0 nitrites, 7.2 ph, and no chlorine. Does this mea it is cycled and I can slowly start adding new fish? How many should I add to this newly established tank at a time? Thanks!