New Koi Floating Upside Down: Shock, Chlorine, or Disease?

Just added a koi and it's floating upside down but still breathing? This is acute stress—usually from transport, water parameter mismatch, or chlorine. Act fast.

Immediate Triage

1. Test pond water NOW: Ammonia, nitrite, pH, temperature, chlorine (if municipal).
2. Check dechlorinator use: Was the pond treated after fill/top-off?
3. Match temperature: Float bag 20–30 min, then drip-acclimate 30–60 min.
4. Add aeration at surface (air stone or pump return).
5. Pond salt 0.1% (if no plants) or 0.05% (with plants) to reduce osmotic stress.

Common Causes

Cause	Signs	Fix
Chlorine/chloramine burn	Gasping, erratic swimming, then listing; gills red/inflamed	Dechlorinator immediately; aeration; salt
pH/temp shock	Immediate listing after release	Slow acclimation; stable parameters
Ammonia/nitrite spike	Multiple fish affected; red gills	Water change; bacteria; stop feeding
Pre-existing illness	Only new fish affected; others fine	Quarantine; treat specifically

Quarantine Is Non-Negotiable

All new koi need 4+ weeks in a separate system. This one went straight to pond—high risk.

If It Doesn't Recover in 24 Hours

• Move to hospital tank with pristine water, salt, aeration.
• Consider clove oil euthanasia if no improvement—prolonged suffering is cruel.

Most upside-down koi from acute shock recover if water is perfect and stress is reduced immediately. Chlorine is the #1 silent killer.