Hi, I have change my Aquaone 620 tank to a salt water one, it has now been cycling for 8 weeks with coral rock in it (4 small pieces) I`m on rain water so nitrite level was 0 ppm on set up, at 3weeks it was between 0.25 & 0.50 going down to 0.25. and just sat on that for 3 weeks. I have done a 25% and 15% water change after 6 weeks but it goes back up to the 0.25 in 2 days. The PH is 8.2 and has not altered.