My nitrites were high for about 4wks, and two of those weeks I had allot of diatoms(brown algae). Then one day my nitrites dropped to zero. It happend fast.
My nitrates never rose. But, over the course of my cycle I had added 30lb LR to my 46g tank, and a 10g sump holding another 15lb LR and 20lb LS. I also used raw shrimp instead of fish to cycle. The combination may explain the zero nitrates.