TheFritz Nitrite Test Kitis a liquid reagent test for measuring nitrite (NO₂⁻) in freshwater and saltwater aquariums. Nitrite is the second toxic compound to spike during a tank’s nitrogen cycle and is lethal to fish even at low concentrations — testing for it weekly (and daily while cycling) is essential. Pair with our other water testing kits and water care supplies.
Why Test Nitrite
- Critical during cycling— nitrite spikes between the ammonia and nitrate phases of every new tank’s cycle
- Toxic at low levels— even 0.25 ppm can stress and kill sensitive fish
- Diagnose a stalled cycle— persistent nitrite means your biological filter isn’t fully established yet
- Should always read 0 ppmin a fully cycled, healthy tank
Specifications
| Brand | Fritz Aquatics |
| Tests For | Nitrite (NO₂⁻) |
| Test Type | Liquid reagent + color comparator |
| Water Type | Freshwater & saltwater |
| Target Reading | 0 ppm in a cycled tank |
Recommended Pairings
- Fritz Ammonia Test Strips
- Fritz GH Test Kit
- Browse all water testing kits
- Water care & maintenance
FAQ
My nitrite is reading above 0 — what now?
Do an immediate water change (25–50%) and add a dechlorinator that detoxifies nitrite (like Fritz Complete). If you’re still cycling, continue dosing ammonia and testing daily until both ammonia and nitrite read 0 and nitrate is showing.
How often should I test?
Daily during fishless or fish-in cycling. Weekly for established tanks. Anytime you spot fish flashing, gasping, or unusual behavior.
Are liquid tests really more accurate than strips?
Yes — significantly. Strips work for quick screens but liquid is what you want for diagnosing real problems.
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