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Cycle Chemistry
Nitrite (NO2-)
The second stage of the nitrogen cycle - less immediately toxic than ammonia but still deadly, causing "brown blood disease" by preventing oxygen uptake.
Unit: ppm Code: NO2
📖 Overview
Nitrite is produced when Nitrosomonas bacteria convert ammonia. It is then converted to nitrate by Nitrobacter and Nitrospira. During cycling, nitrite spikes for 2-3 weeks between the ammonia and nitrate stages. Nitrite binds hemoglobin, forming methemoglobin, which cannot carry oxygen - suffocating fish from within ("brown blood disease").
📉 How to Lower
Water changes. Salt (chloride ions compete with nitrite uptake). Ammonia detoxifier products often neutralize nitrite too. Time - the cycle will complete.