So if I’m understanding you correctly, the original ammonia was processed, but that nitrate was consumed by other microorganisms, rather than just staying in the water?I can think of several reasons why nitrate did not show when you dosed ammonia, and IMO, it reflect the problems of using nitrate as a gauge of cycling. Simple consumption and incorporation of the N into bacteria and other microorganisms and algae could explain why a few ppm ammonia didn't result in nitrate.