Winterization and Cold Weather Care

Proper winter preparation is critical for koi survival in cold climates. Start preparing 4-6 weeks before your first expected freeze.

Temperature milestones:

Below 65F: Switch to wheat germ food

Below 50F: Stop feeding entirely

Below 40F: Koi enter torpor (hibernation-like state) at the bottom

Winter preparation checklist:

Install leaf netting before autumn leaf fall

Perform a large water change (30-50%) while temps are still above 60F

Clean the pond bottom of debris and organic matter

Switch to wheat germ food, then stop feeding below 50F

Remove and store UV sterilizer indoors

Install a de-icer or floating heater to maintain an opening in the ice

Add or maintain an aerator for gas exchange

Reduce or redirect pump flow away from the bottom (where koi rest)

Critical winter rules:

NEVER break ice by striking -- shock waves can injure or kill fish

Maintain at least one opening in the ice for gas exchange (toxic gases must escape)

Pond should be at least 3-4 feet deep for safe overwintering

Shallow ponds in cold climates may need to bring fish indoors

Spring restart:

Do not rush to feed -- wait until water temperature is consistently above 50F

Perform a water change and test all parameters

Restart UV sterilizer and resume normal filtration

Begin feeding wheat germ food in small amounts