Before I continue I must comment... Your avatar is awesome!

Quote Originally Posted by jrlevers
Does anyone know if growing peas and other nitrogen fixing plants such as beans affect nitrite levels? My system is two months old and I'm having issues with unreadable nitrite levels. Last test: Ammonia 0, Nitrite > 5, Nitrate 160. Temp 82 and pH 7.8.

My tilapia are starting to suffer and no matter how many water changes I do I can't seem to get my Nitrites down. I have peas, beans, yellow peppers and lettuce growing (14 plants) and duckweed.

I have recently increased the amount of feed they're getting because they're approaching 4 inches.

Any advice?
The nitrite is coming from either the ammonia or the nitrate. Typically, it flows from ammonia to nitrite to nitrate, but in anaerobic conditions it may flow from nitrate back to nitrite. Any spots that accumulate a lot of organic matter with little water movement could be breeding grounds for some anaerobic bacteria.

Otherwise, the legumes (beans and peas and such) are not your source of nitrite. Nitrogen fixation from these plants/bacteria yield ammonia.

N2 + 8 H+ + 8 e? ? 2 NH3 + H2