Heone Fish Water Test Kit NO2

Testing NO₂ (nitrite) is important because it shows whether toxic nitrogen compounds are being properly broken down in your aquarium’s biological filtration.

Nitrite is produced after ammonia is broken down, and it is still very harmful to fish even at low levels.

It helps you:

• Detect dangerous nitrite buildup during cycling or filter issues
• Prevent oxygen starvation in fish (nitrite affects blood oxygen transport)
• Monitor whether beneficial bacteria are fully established
• Avoid fish stress, lethargy, and sudden losses
• Ensure the nitrogen cycle is working properly

In short, nitrite should always stay at 0 ppm — any reading means your tank is not fully safe yet.