Ok just got my checkers today and tested my tank and freshly filtered rodi water. I have been battling cyano now for about 4-6 weeks. It's mostly on the sand and some rocks. Tank tested 0.15ppm and rodi tested 0.37!!! I have no livestock other than snails. I lost everything to Sandy back in October. I just started running biopellets a week ago. I've had lights out for about a week. Cyano is dying off. Maybe that is causing high phos levels. I just refuse to stock anything until this cyano is gone. This is becoming very discouraging. Any help or suggestions. I almost at the point of breaking down this tank and getting out of the hobby after 8 years.