patrickkwan wrote: ok.thx so much.because my other tank do not like it.they also go back to 0.so i want to know is the n-cycle finish or not.now i understand.but i also want to know how about the ORP. because i see the tank have the ¬Á¼þÂÎ.i know it is not a big problem.i think the tank have ¤j¶q¦³¾÷ª«.but i always add the PSB and i have use O3.the ORP also is so low.can't increase.i have ´«¤ô once a week.but i feel the ¤ô½è also not stable.¬Á¼þÂÎ also here.¬Á¼þÂÎuntil now around 3 week.what can i do?or how long the ¬Á¼þÂÎ will decrease or dead?how can make the ¤ô½è better?