Koi Deaths After Hailstorm: What to Do

Hailstorm Impact

Two 5-min hailstorms 45 min apart. Next morning: pond filthy, fish stressed. Largest koi (18″, 5 lbs) dead in skimmer. Two more dying (one wedged, one rolling). Survivors huddled under shelter rock.

How Hail Kills Koi

• Rapid temperature/pH drop from ice melt.
• Physical trauma from hailstones.
• Contaminants in hail (atmospheric pollutants).
• Fish striking surface thinking hail is food.

Emergency Care

1. Partial water changes: ⅓ volume daily for 3 days. Add Stress Coat, pond salt (non-iodized), beneficial bacteria.
2. Maximize aeration: Run waterfall, add air pump with stones.
3. Do not feed until fish act normal.
4. Remove dead fish immediately to prevent ammonia spike.

Prognosis

Monitor for 2 weeks. If survivors eat, swim normally, and show no lesions, they'll likely recover. Secondary infections (fungus, bacteria) are common post-trauma—treat promptly if seen.

Prevention

Install hail netting or a sturdy canopy over pond before storm season.