WATER PROBLEMS
Ammonia
If ammonia is not zero, treat it as urgent—especially in warm water or when fish are already stressed.
What it is
Ammonia is a toxic waste product that builds up when the biofilter can't keep up (new pond, filter disturbance, overfeeding, die-off, heavy stocking).
What you may see
- Gasping, hanging near returns or air
- Flashing/rubbing, clamped fins
- Lethargy, loss of appetite
- Gill irritation (sometimes)
What to do now (order matters)
- Increase aeration immediately.
- Water change (use a dechlorinator for all new water).
- Detox/bind ammonia to reduce toxicity while your filter catches up.
- Stop feeding temporarily if readings are elevated.
- Re-test in a few hours, then daily until stable at 0.
Why it happened
- New pond start-up / immature biofilter
- Filter cleaned too aggressively (biofilm removed)
- Power outage (biofilter die-off)
- Overfeeding or sudden increase in fish load
- Hidden rotting debris
When to escalate
- If fish are rolling or in severe respiratory distress: treat as an emergency (aeration + larger water change + detox).
- If symptoms persist after ammonia stays at 0: move to symptom-first triage on SickKoi.com.