¤_ 2007-03-26 11:38 I don't know why the N-cycle of my new tank have some problem.My tank size is 30"X16"X18".I start the N-cycle on 27-12-06.At the start of FEB.NH3 go back to 0.1ppm.but at that time NO2 and NO3 is very high.But at the end of Feb. No2 and No3 start to below.But can't go back to 0.NO2 keep at around 0.3ppm and NO3 keep at around 10-20ppm.The numble keep at that time until now.And i check the ORP just keep the number around 200-230. Cannot go higher. ¹LÂo»ö¾¹:Via-Aqua 750 Âo±í(two layer of ¥Íª«Àô in Âo±í,one layer of ¹LÂo´Ö) around 3"-4" ¨F§É & Powerhead ¼ç¤ô¬¦ 1500L/H Weipro 2011 ³J¥Õ¤ÀÂ÷¾¹ I think it is enough place for N-cycle.But i really don't know why the NO2 and No3 can't go back to 0.Can you answer me where i have wrong?Why i have the N-cycle and ORP problem?