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What do nitrifying bacteria turn nitrite into?

Nitrate, a much less harmful form of nitrogen.

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  1. Ammonia
  2. Nitrate ✔
  3. Nitrogen gas

Why: The second group of nitrifying bacteria oxidizes nitrite to nitrate. Nitrate is far less toxic than ammonia or nitrite.

Huh, didn't know that: Aquarium filters should grow both groups of bacteria.

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References

Answer: Nitrate. The second group of nitrifying bacteria oxidizes nitrite to nitrate. Nitrate is far less toxic than ammonia or nitrite.

  1. UF/IFAS Extension FA031: Ammonia in Aquatic Systems edis.ifas.ufl.edu/publication/FA031
    Other groups of bacteria, including Nitrospira and Nitrobacter (and collectively called nitrite-oxidizing bacteria [NOB]) convert nitrite to the much less toxic nitrate
    Checked 2026-10-11.

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