Koi in Distress After Snow Buried Pond

600-gal NE pond, 3 ft snow drift covered pond for 3 days. Deicer/aeration ran. One 18-inch koi found on side, breathing, gills moving. Moved to quarantine tank at 38°F. Other fish healthy on bottom.

What Happened

Snow burial caused darkness + potential CO₂ buildup + temperature stratification. The affected koi likely surfaced seeking oxygen, got trapped in ice/slush, and suffered cold shock + swim bladder dysfunction (common <48°F).

Correct Quarantine Protocol

1. Use pond water (not tap) in quarantine tank.
2. Raise temperature SLOWLY: 1–2°F per hour max. Target 50–55°F.
3. Dark, quiet location—minimize stress.
4. Gentle aeration, mature filter media, no feeding initially.
5. Small daily water changes (10%) with temperature-matched pond water.

Critical Winter Rule

Do not shovel snow off pond. Snow insulates. Removing it causes rapid cooling and stresses fish. Let deicer/aeration work. If pond is frozen, melt a hole with hot water—never chop ice.

This koi may recover with slow warming and rest. The others survived because they stayed deep and inactive.