Nitrogen Cycle Tracker
Before adding fish to a new aquarium, the tank must go through the nitrogen cycle — a biological process that establishes colonies of beneficial bacteria capable of converting toxic ammonia into harmless nitrate. This tracker logs your daily test readings and tells you exactly where you are in the process, with specific guidance on what to do next.
Nitrogen Cycle Tracker
Cycle progress
Ready to begin
Tank set up, dechlorinated water added, waiting for ammonia dose. Add pure ammonia to reach 2–3 ppm to start the cycle.
Ammonia active
Nitrite appearing
Nitrite peak
Cycle completing
Tank cycled ✓
Waiting for first reading
Log your water parameters using the form to start tracking your cycle's progress.
What happens next
- 1Add dechlorinated tap water and ensure temperature is 25–28°C.
- 2Add pure, unscented ammonia to reach 2–3 ppm.
- 3Test ammonia in 24 hours to confirm your dose.
- 4Do not add fish, plants, or bacteria supplements yet.
Log a reading
Your readings save automatically — bookmark this page and return daily.
What you'll need to cycle your tank
The API Master Test Kit is essential — liquid tests are far more accurate than strips for detecting the low levels that matter during cycling.
Tests ammonia, nitrite, nitrate, pH, and high-range pH — everything needed to track a complete nitrogen cycle
Concentrated nitrifying bacteria — seeds your filter media and accelerates the first weeks of cycling
Pure ammonia source for fishless cycling — more consistent than household ammonia, no surfactants
I’ve used everything listed in my own tanks. If you buy through a link, I earn a small commission — at no extra cost to you, and it never affects what I recommend.
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Frequently Asked Questions
- How long does fishless cycling take?
- A fishless cycle typically takes 4–8 weeks from the first dose of ammonia to a fully established colony. Several factors affect timing: water temperature (bacteria grow fastest at 25–28°C), pH (activity slows significantly below 6.5), whether you used a bacterial supplement to seed the filter, and ammonia dose consistency. Tanks cycled at low temperatures or without seeding can take 10–12 weeks. The tracker above estimates remaining time based on your current stage and readings.
- How much ammonia do I add for fishless cycling?
- Dose pure, unscented ammonia to reach 2–3 ppm on day one. This is enough to feed Nitrosomonas bacteria without inhibiting the second group (Nitrospira) that converts nitrite to nitrate. Keeping ammonia above 5 ppm throughout the cycle can stall nitrite conversion. Use only pure ammonia — check the label for surfactants or perfumes, which will foam and harm bacteria. Redose when ammonia drops below 1 ppm during the cycle.
- Why is my nitrite not dropping?
- The three most common causes are low pH (below 6.5 significantly slows Nitrospira bacteria), low temperature (below 20°C cuts bacterial activity substantially — aim for 25–28°C), and too much ammonia (above 4–5 ppm inhibits the nitrite-oxidising bacteria you need). A very high nitrite spike (above 5 ppm) can also slow progress. If this is your issue, do a 25–30% water change to reduce nitrite below 3 ppm, then continue dosing ammonia. If you've had no movement in over two weeks, check you have adequate flow through your filter media — bacteria colonise surfaces, not open water.
- When is my aquarium fully cycled?
- Your tank is fully cycled when both ammonia and nitrite drop to near-zero (below 0.25 ppm) within 24 hours of dosing 2 ppm of ammonia. This confirms that both Nitrosomonas and Nitrospira bacteria are established in sufficient numbers to handle a fish load. Run this test twice on consecutive days before adding fish. Once confirmed cycled, do a 50–70% water change to bring accumulated nitrate below 20 ppm, then add your first fish gradually.
- What do I do after the tank is cycled?
- First, do a large water change (50–70%) to reduce accumulated nitrate to below 20 ppm. Test once more to confirm ammonia and nitrite are still at zero. Then add fish gradually — a third of your planned stocking in the first week, another third two weeks later. Continue testing twice a week for the first month to confirm your filter handles the growing bio-load. Avoid overstocking in the first few months while the bacterial colony sizes up to match the fish waste.