When is a tank considered cycled?

A tank is cycled when ammonia and nitrite both read 0 ppm while nitrate is present and rising. That means your bacteria can convert toxic ammonia all the way to relatively harmless nitrate within 24 hours. The tracker flags this state as Complete.

What are the phases of the nitrogen cycle?

First ammonia rises as waste accumulates. Then ammonia-oxidising bacteria appear and nitrite climbs while ammonia falls. Finally nitrite-oxidising bacteria establish, nitrite drops to zero, and nitrate accumulates. The tool labels which phase your latest reading matches.

How long does cycling usually take?

A fishless cycle typically takes four to eight weeks at normal room temperature. Warmer water, an established filter media seed, or bottled bacteria can shorten it considerably. The estimate here is a rough guide from your own trend, not a guarantee.

Should I do water changes while cycling?

During a fishless cycle you generally avoid large water changes so the bacteria have a steady food source, unless ammonia or nitrite spike very high. If fish are present, change water whenever ammonia or nitrite exceed safe levels to protect them.

Why is my nitrate so high at the end?

Nitrate is the end product of the cycle and is not removed by bacteria. Once cycled, regular partial water changes keep nitrate in a safe range, typically under 20 to 40 ppm for most freshwater community tanks.

Aquarium Nitrogen Cycle Tracker

Cycling a new aquarium means waiting for two colonies of beneficial bacteria to establish before adding fish. This tracker turns your daily test-kit readings into a clear picture of which phase you are in, whether the cycle has finished, and roughly how long is left.

How it works

The nitrogen cycle has three measurable phases, identified from the latest reading:

Ammonia phase : ammonia rising,  nitrite ~0, nitrate ~0
Nitrite phase : ammonia falling, nitrite rising
Complete      : ammonia = 0 AND nitrite = 0 AND nitrate > 0

The days-remaining estimate looks at how fast ammonia and nitrite are falling across your two most recent readings and projects when both should reach zero. A falling trend gives a finite estimate; a flat or rising trend means the cycle has not yet turned the corner.

Tips and notes

Use a liquid reagent test kit rather than strips for accuracy at low concentrations. Test at the same time each day for a consistent trend. Keep the water warm (around 26 to 28 C) and well-oxygenated to speed bacterial growth. All your readings stay in this browser, so you can log over weeks of cycling and revisit the trend at any time without an account.