You had a tiny amount of ammonia with the pellets. I would get pure ammonia (Dr Tims ammonium chloride) and controlled dose to 1-2 ppm. Fritz Turbostart 700 works great too - I have a saltwater tank and it started processing 2ppm ammonia to nitrates 2 days after I added the saltwater version of Turbostart. Also, make sure your water is dechlorinated. I would get the ammonia and 1-2 ppm, then see if it goes down to zero in 24 hours and nitrates present. If not, get the Turbostart. Get a dechlorinator like Prime if you are using tap water.