Fritz Nitrite Test Kit
Nitrite is produced continually during the ammonia cycle by nitrifying bacteria in the biological filter. While not as immediately toxic as ammonia, any accumulation of nitrite should still be addressed as soon as possible. The nitrite level will eventually be broken down to non-toxic nitrate. Regular testing for nitrite is recommended – chronic exposure to even low levels of nitrite can cause brown blood disease in fish, which can cause suffocation and death.
With the exception of a system establishing a biological filter and progressing through the nitrogen cycle, the nitrite level in any tank should ideally be zero.
Directions
- To remove childproof safety cap, push down while turning.
- Fill a clean test tube with 5 ml of water to be tested (to the line on the tube).
- Add the appropriate reagent from the kit as instructed.
- Wait for the color change to appear and compare with the color chart provided.
| Parameter | Value |
|---|---|
| Test Type | Nitrite |
| Test Volume | 5 ml |
| Detection Range | 0 – 50 ppm |
| Accuracy | ±10% |
| Storage | Store in a cool, dry place away from direct sunlight |
FAQ
How often should I test my tank for nitrite?
It is recommended to test for nitrite at least once a week, or more frequently during the initial cycling phase or if you notice changes in fish behavior or health.
Can this test kit be used for both freshwater and saltwater tanks?
This test kit is designed for freshwater aquariums. It is not suitable for saltwater systems.
What does a positive result indicate?
A positive result indicates the presence of nitrite in the water. Even low levels can be harmful to fish over time, so it’s important to take corrective action if nitrite is detected.

Peter Jones –
The test kit is easy to use and gives clear results. I’ve been using it weekly since setting up my tank and it helps me catch nitrite spikes early. The color chart is accurate and the instructions are straightforward.
Diana Kerr –
Works well for regular monitoring. I noticed a small nitrite spike after adding new fish, and I was able to adjust my water changes promptly. The only thing missing is a digital reader, but the visual method is reliable.
Penelope Piper –
Very reliable for detecting nitrite. I’ve used it for over six months now and it has helped maintain stable water conditions. The test tube is easy to clean and the reagents stay effective for a long time.