A Seasonal Guide to Keeping Your Koi Healthy from Fall to Spring
As the seasons shift and temperatures drop, it’s essential to ensure your koi pond is ready for the colder months ahead. Proper seasonal preparation will help protect your koi from harsh conditions and promote a healthy transition into spring. Whether you’re a first-time pond owner or an experienced hobbyist, this guide will walk you through fall prep, winter care, and spring maintenance—so your koi can thrive all year long.
Fall Pond Care: Laying the Foundation for Winter
Fall is the most critical time to begin preparing your koi pond for winter. Taking a few proactive steps now will save you time and stress later—and keep your koi healthy and safe.
Remove Pumps and Water Features
As temperatures start to drop, remove your water pumps, including waterfall and fountain features. This halts water circulation and allows a “warm zone” to form at the bottom of the pond where koi can comfortably hibernate. Store your equipment indoors to prevent freeze damage.
Clean Out Debris
Falling leaves, dead plants, and twigs can quickly decay and harm your pond’s water quality. Decomposing organic material releases harmful ammonia and consumes oxygen—two things your koi don’t need in winter. Clean your pond thoroughly and consider installing a pond net to prevent future leaf buildup.
Adjust and Stop Feeding
As the water temperature dips below 65°F, start reducing how much you feed your koi and switch to a cold-water formula to ease their digestion. Once the water consistently stays below 48°F, stop feeding completely. Koi naturally slow their metabolism and don’t require food during winter hibernation.
Winter Pond Care: Keeping Your Koi Safe in the Cold
Once winter sets in, your koi enter a semi-dormant state known as torpor. While they don’t need much attention, there are a few things you should still monitor.
Is My Pond Deep Enough?
Depth is more important than temperature. Koi can safely hibernate in ponds at least 3 feet deep. Deeper ponds offer a stable thermal layer where water remains above freezing. If your pond is shallow or raised above ground, consider moving your koi indoors for the winter.
Prevent Ice Build-Up
When a pond freezes over, toxic gases from decaying material can build up and reduce oxygen levels. To prevent this, install a pond de-icer to keep a small opening in the ice. Pair it with an aerator to improve oxygen exchange and circulation under the ice. The air stone of the aerator also should be kept near the surface to churn the surface water and keep the ice from freezing solid.
Avoid Feeding
Even if you see your koi swimming on warmer days, do not feed them during winter. Their digestive systems are shut down and feeding them can cause health issues.
Spring Pond Care: Waking Up After Winter
As winter fades, it’s time to reawaken your pond and prepare it for the active months ahead. This season is all about cleaning, monitoring, and helping your koi ease back into feeding and swimming.
Spring Cleaning
After months of inactivity, your pond needs a deep clean. Remove debris, algae, and clean all pond equipment—especially your filters, pumps, and UV lights. Even if your UV bulb is still shining, replace it annually for maximum effectiveness. UV light plays a critical role in reducing algae and harmful bacteria in early spring.
Monitor Water Quality
Spring brings an explosion of new bacteria and algae growth, so it's vital to test your water regularly. Check for ammonia, nitrites, nitrates, and pH balance. You can also reintroduce aquatic plants to help with natural filtration.
Reintroduce Feeding Slowly
Once the water temperature is consistently above 45°F, you can begin gradually reintroducing food. Start with small amounts of cold-water koi food to help them adjust as their digestive systems slowly restart.
Should You Bring Your Koi Indoors For Winter?
If your pond is too shallow or at risk of freezing completely, it’s safer to relocate your koi indoors. An indoor tank must have both mechanical and biological filtration as well as being aerated. It is important to closely monitor the water quality of an indoor tank, especially if it is significantly smaller than your outdoor pond as it is more likely to have changes in water quality. Click here for an article with further information about keeping koi indoors.
Have Questions About Koi In Winter?
We’re happy to help! If you need any guidance or have any confusion about preparing your Koi for winter, or reintroducing them to spring, feel free to contact our knowledgeable team for further elaboration and details about caring for Koi in the cold.
