SO, I have a 29 gallon freshwater tank, artificial plants, gravel substrate. I had a school of 6 tiger barbs, a yellow molly and a silver molly, and a few ghost shrimp. I did a 25% water change, then reached into the tank with the WRONG cleaning brush to knock some algae off of a rock.
Yes, amateur move. Anyway, within about 10 minutes all the fish were dead, I'm pretty sure the brush had some residual household cleaner on it. I flushed the tank with clean, dechlorinated water several times, and changed the filter media. I did not remove any substrate or decorations. Added new water and tested ammonia. I had ammonia readings of ~0.5ppm (which was the same as the tap water). I tested daily, and at the end of 3 days, ammonia and nitrite readings were 0. I cautiously added 3 serpae tetras 5 days ago, and started testing for ammonia daily to monitor the new cycle. The fish are happy, not stressed, and are doing fine.
So finally, here is my question: I continue to have readings of 0ppm ammonia, and 0ppm nitrite. I do have a nitrate reading of <20ppm. Why is my tank not cycling?? Do I need to add more fish? Could my bacteria have re-established that fast from the substrate and decorations??
Thanks in advance for your help! And yes... I will label my cleaning containers from now on...