I dunno is it right anot.. but to my understanding it only break down ammonia before it turn to nitrate. so if ur tank is a mature tank, hydra will convert ur ammonia but ur existing nitrate will still be there unless u export it with wc, plant or run on zeovit ba.. unless it a new tank with zero nitrate, then the ammonia nv have a chance to turn nitrate and ur nitrate will always stay at zero..