My 16g tank has been going for 4 months. The first two weeks were spent searching fruitlessly for ammonia. I then put a few of plants in and added four or five fish. I owned the API liquid test kit and it was current. (and I also know it worked because at the time I had a Betta in a bowl - now in his own aquarium) I faithfully checked ammonia and nitrites daily at first and did 25% - 30% water changes. After a couple of weeks I tapered off to every other and then every third day. That was it. I finally changed to just checking the chemistry and changing about 25% of the water every 5 - 7 days. Only one day did I get an ammonia ready of .25ppm, never any nitrites. At about 31/2 months I started to get nitrates. Traces at first and then finally up to 20ppm. I got 40ppm one day recently and immediately changed out some water, pruned the dead plants and got it back to 20ppm. Everyone says once you see nitrates your tank it is cycled. All fish are fine. Can you cycle a tank without ever having a reading for ammonia or nitrites?? Oh, and for the last month it has been fully stocked, the 3 fry that didn’t get eaten are growing rapidly and the two otos that I actually didn’t consider part of the stocking are fine.
