Ammonia is an immediate warning
Fish excrete ammonia and decaying food adds more. Any detectable reading in a stocked system deserves verification and prompt action.
Nitrite signals incomplete processing
Nitrite can rise when the second stage of biological filtration is insufficient or disturbed.
Nitrate shows accumulation
Nitrate is generally less acutely toxic than ammonia or nitrite, but increasing levels reveal the balance between feeding, filtration, plants and water changes.
Respond to the cause
- Verify the test and source water.
- Reduce or pause feeding as appropriate.
- Remove dead organisms and excess food.
- Check filter flow and oxygenation.
- Perform matched, conditioned water changes.
- Add mature filtration rather than unseeded media alone.
Record the event
Note the date, feeding change, maintenance and result. Repeated spikes mean the system or workload is undersized.