The Short Answer: Colder Than You Think
Koi are tougher than they look. While they prefer water between 65°F and 75°F, they can handle temperatures down into the mid-40s, as long as your pond stays oxygenated and clean.
In Arizona, it’s rare for ponds to get that cold, but sharp temperature swings between warm days and cold nights can still stress your fish.
🌡 Understanding Koi Behavior in Winter
When the water cools below 60°F, koi start to slow down. Below 50°F, they enter a semi-dormant state, moving less, eating less, and conserving energy.
This is completely normal, but it means you need to adjust how you care for them.
🍽 Feed Smart, Not Often
Switch to Aquascape Cold Water Fish Food as soon as temps drop below 60°F. Feed small amounts every few days, and stop completely below 50°F. Uneaten food can rot, raise ammonia levels, and stress your fish.
💡 Pro Tip: Always feed when the sun is highest, midday feeding gives koi the best chance to digest before the water cools overnight.
💨 Keep Oxygen Flowing
Cold water holds more oxygen, but koi still need circulation. A pond aeration system or a small Aquascape waterfall pump keeps the surface from stagnating.
If ice ever forms (rare here!), the aerator helps gases escape and maintains oxygen flow.
🪵 Provide Shelter
Add koi caves, aquatic plants, or large rocks where your fish can rest and feel secure. These features also help regulate temperature swings.
🧪 Monitor Water Quality
🧘 Let Nature Do Its Thing
If you’ve done your fall prep, clean water, steady flow, balanced bacteria, your koi will rest peacefully all winter long and greet spring strong and healthy.
Ready for Winter? Let Us Help Your Koi Thrive
Keep your koi happy through Arizona’s cooler months! PondscapesAZ provides seasonal koi pond maintenance, aeration installation, and Aquascape care services to keep your pond thriving year-round.
Give us a call at 480-987-7781 or contact us online to schedule service for your koi pond in Scottsdale!
Owner, Lead Designer
Ralph Biezad is the owner and lead designer of Pondscapes, a premier pond and water-feature design-build company based in Gilbert, Arizona. With more than 25 years of experience, Ralph has created hundreds of custom ponds, waterfalls, and aquatic landscapes throughout the Southwest. His philosophy centers on designing natural-looking, low-maintenance environments that blend seamlessly with Arizona’s climate and terrain.
As a Certified Aquascape Contractor, Ralph is recognized nationwide for his craftsmanship, creativity, and commitment to eco-balanced water features. His designs emphasize sustainability, habitat creation, and bringing clients closer to nature through water.
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