What the measurements describe
UF/IFAS describes bacteria converting ammonia to nitrite and then nitrate, with oxygen needed along the way. Its startup guidance calls for daily ammonia, nitrite, pH, temperature and alkalinity measurements to follow the rise and fall. Calendar age and clear water cannot show that this has happened.
Use a fishless cycling plan appropriate to your equipment. This page interprets the test sequence; it does not supply an ammonia dose or recommend adding fish to produce waste.
Which readings, on which days?
- On the day you start: log the source water and tank results, kit, units, pH and temperature. Zero readings in newly filled water do not show an established biofilter.
- Every day during cycling: test ammonia and nitrite, and record nitrate alongside them. Keep the planned waste input and water changes in the log. Look for processing of that input, not merely dilution after a water change.
- After the peaks: ammonia and nitrite should return to zero on the kit’s scale. Nitrate production is supporting evidence; source water may already contain nitrate, and plants can consume it.
- The day before and the day you intend to add fish: recheck that both ammonia and nitrite remain undetectable under the ongoing cycling plan. This is our cautious final check, not a UF/IFAS two-day guarantee. A fresh tank with no waste input can also read zero.
There is no universal “ready on day” number. These results support biofilter readiness for the load it has processed, not every future fish load. Separately confirm species requirements and a suitable introduction plan. Continue testing after any introduction; a new rise means the load is not being handled.
Prepare the equipment and instructions
- A complete filter, installed and operating according to its manual.
- The tests required by the cycling plan, with instructions, expiry information and clean sampling equipment.
- A separate thermometer and the applicable water-preparation instructions.
- A place to log observations and changes to the setup.
The API Freshwater Master Test Kit measures pH, high-range pH, ammonia, nitrite and nitrate. It does not supply every water test a care plan might call for. Compare what each kit measures before relying on the word “master”.
Keep a useful cycling log
| Write down | Why it belongs beside the result |
|---|---|
| Date and sampling point | Distinguishes a trend from one sample. |
| Parameter, result and units | Keeps ammonia, nitrite and nitrate distinct. |
| Kit and method | Lets you interpret the result using the matching instructions. |
| Temperature and pH | Preserves conditions relevant to interpreting ammonia. |
| Recent changes | Notes water changes, filter work and additions without guessing a cause. |
UF/IFAS recommends retaining test results and watching trends. A single sample cannot reconstruct conditions before it was taken.
What if the readings are not ready?
| Pattern | What to do next |
|---|---|
| Ammonia or nitrite remains detectable | Do not add fish. Continue daily tests. Check the running filter, water movement, aeration, pH and alkalinity; follow the cycling plan’s instructions before changing its inputs. |
| All three tests are zero, with no known waste input | Readiness is not demonstrated. Verify the test procedure and the cycling plan. Do not invent a challenge dose. |
| Nitrate is present but ammonia or nitrite is also present | The full process is not yet keeping up. Nitrate alone is not a pass. |
| Readings rise after filter work, an outage or adding fish | Pause further additions. Check what changed and restore correct equipment operation. Keep the test history. |
If fish are already present and ammonia is detected, UF/IFAS advises reducing or stopping feeding and using water changes as appropriate. Its feeding guidance has an exception for fry, which require frequent food; obtain qualified advice for that situation. Test replacement water too and prepare it correctly. Do not add ammonia to an occupied tank. For distress or unresolved water-quality problems, contact an aquatic veterinarian promptly with the log; a calculator cannot diagnose the cause.
Check interrupted circulation, follow the exact test method, or calculate a water-change amount you have chosen.