I am reading 0 ammonia, nitrites, and nitrates. My phosphates are around .01 as read by a hanna checker. The tank is only 10 months old and has very few inhabitants (2 clowns, 1 tang, 1 small wrasse, assorted CUC). The sand is new but the rock I got from someone else, the only thing I can think of at this point is maybe it needs to be cooked to release anything pent up in the rock.