Thats good news. You may well be cycled for those 4 fish, but when you put more stock in you will have a mini cycle until the bacteria build up again.I haven't done a water change for over a day and I'm still at 0ppm for ammonia and nitrites......I'll get happy if it is the same tomorrow!!!
Yes, as long as your dechlorinated tap water has less ammonia in it.I had a possible faint shade of green in my ammonia test this morning....should I do a partial water change or let it sit for a day and re-test? Nitrite was 0