Nitrogen Cycle Tracker
Last updated: November 2026
Enter each day's ammonia, nitrite, and nitrate readings (ppm) and this tool builds your cycle log, tells you which phase you're in — ammonia spike, nitrite spike, stalled, or cycled — and answers the only question that matters during a new tank: is it safe for fish yet? Fishless cycling is the fix behind new tank syndrome; this tracker is how you watch it work instead of guessing.
Where your data lives — the honest version
Readings are stored only in this browser, under the fixed localStorage key fishsymptoms.cycleTracker.v1, so your log survives closing the tab and comes back next visit. Nothing is uploaded anywhere and there is no account. That also means: clearing browser data clears your log, and there is no shareable link for a cycle log — this tool keeps no server copy, so we won't pretend a URL can carry your data. To move a log to another device or show someone your numbers, use Print as log or Export JSON.
How the tracker reads your cycle
These are the same phase rules the new tank syndrome timeline is built on, applied to your numbers instead of a textbook table:
| Phase | Rule the tracker checks | What to do |
|---|---|---|
| Early cycling | Ammonia ≤ 0.25, nitrite ≤ 0.25, no nitrate rise yet, under day 7 | Nothing's wrong — it's simply too early. Keep dosing your ammonia source and test every 2 days. |
| Ammonia spike | Ammonia above 0.25 ppm and at or above nitrite | First bacteria colony is building. No fish in this window; do big daily changes if fish are already present (gasping protocol). |
| Nitrite spike | Nitrite above 0.25 ppm and above ammonia | The classic kill zone, ~days 10–21. Nitrate barely started. Test daily once fish are in; 1 ppt salt protects gills if fish are present. |
| Stalled | Both ≤ 0.25 past day 7 but nitrate never appeared or grew | Find the cause: chloramine in dosed water kills the colony, dead-back re-dosing stops, or there was never an ammonia source. Then restart the source and re-log. |
| Cycled | Ammonia ≤ 0.25 and nitrite ≤ 0.25 and nitrate rising | Confirm with the 2 ppm challenge dose (converts to 0/0 inside 24 h), big change, then stock a fraction of your final load — see the stocking calculator. |
Tracker says spike — and you have fish in there?
The tracker is a log, not a rescue. While readings sit above 0.25 ppm with livestock present: 40–50% temperature-matched water change daily, feed nothing above zero, airstone on. The full sequence is the new tank emergency protocol, also as a printable checklist PDF.
FAQs
Where does the tracker store my readings?
In this browser only — localStorage key fishsymptoms.cycleTracker.v1. No server, no account, nothing uploaded. Print or export the log if you want a permanent copy.
When is my tank "cycled" according to this tool?
Ammonia and nitrite both at 0.25 ppm or below while nitrate is rising. Then confirm with a 2 ppm ammonia dose that converts to 0/0 within 24 hours before adding livestock.
Why does it want nitrate "rising" before calling it cycled?
0/0 with no nitrate means nothing is being converted — either nothing is feeding the cycle or the colony died. Nitrate is the footprint of conversion actually happening; that's what distinguishes "cycled" from "stalled".
Can I share my log with someone via a link?
No — and we'd rather say so than fake it. The log never leaves your browser, so there is no link to send. Export the JSON or print the log instead.
My nitrite peaked after ammonia hit zero — normal?
Textbook normal: the nitrite-eating population always lags. Days 10–21 of a fishless cycle is exactly where that nitrite hill lives, with nitrate just starting to climb behind it.
Severe cases: consult an aquatic-experienced vet where available.