What is nitrite in aquariums?
Nitrite (NO₂⁻) is an intermediate compound in the nitrogen cycle, produced when beneficial bacteria convert ammonia from fish waste and decaying matter.
Why nitrite is dangerous
Even small amounts of nitrite are harmful to fish:
- Interferes with oxygen transport in the blood (methemoglobinemia)
- Causes stress, lethargy, and gill damage
- Can lead to death if levels remain high
Safe levels
- 0 ppm is the target for all aquariums
Nitrite in the nitrogen cycle
Monitoring nitrite is crucial during new tank cycling and after major tank changes.
How to reduce nitrite
- Perform partial water changes
- Ensure the tank is fully cycled
- Avoid overfeeding and overstocking
- Use biological filtration to support nitrite-converting bacteria