Don't let Fall and Winter Wreck Your Pond: A Minnesota Guide for End of Season Prep
When spring arrived in Lakeville, Jim and Carol were excited to restart their pond after a long Minnesota winter. But when they went to plug the pump back in come Spring, their excitement quickly turned to disappointment. Piles of soggy leaves had collected at the bottom, turning into a foul-smelling sludge that clouded the water and was a nightmare to clean out. And as they began refilling the system, they noticed the waterfall wasn’t circulating properly. After some inspection, the real culprit emerged: a cracked water line buried underneath a massive boulder. Accessing the break required bringing in heavy equipment just to move the rock and reach the connection to the waterfall’s biofalls.
What could have been a smooth spring startup turned into a major repair project—expensive, messy, and stressful—all because the pond hadn’t been prepped for fall and winter.
Stories like Jim and Carol’s are all too common in Minnesota. Our climate puts unique stress on water features, and without preparation, ponds can quickly turn from peaceful retreats into winter disasters. This guide walks you through exactly what to do this fall so your pond is safe, your fish are healthy, and your spring startup is stress-free.
1. Netting Your Pond in the Fall
The first step in winter prep begins before the snow falls. Autumn leaves and windblown debris might look harmless, but once they sink, they start decomposing, releasing nutrients that fuel algae blooms and create oxygen-depleting muck that can kill your fish over our long winter.
A simple pond net can catch most of this debris before it settles. The Minnesota Pollution Control Agency notes that excess organic matter is one of the leading contributors to poor water quality in small water bodies (MPCA, 2023). By netting early, you save yourself major cleanup work later and protect fish from low-oxygen conditions under the ice. Nets also deter raccoons and birds during fish dormancy.
Many pond owners underestimate just how much debris falls in autumn—especially if you have mature trees nearby. Even “a few” leaves can turn into pounds of decomposing waste by spring. Installing a pond net in September/October and leaving it in place until the leaves are down is one of the most cost-effective, protective steps you can take for the health of your system and fish. It’s the difference between a quick spring startup and a major drain-and-clean muck-out service.
2. Slowing—and Then Stopping—Fish Feeding
Minnesota ponds freeze fast, and so do the metabolisms of fish. Once water temps dip below 55°F, digestion slows to a crawl. Feed lightly, and by 50°F, stop feeding entirely. Uneaten food and fish struggling to digest protein lead to health risks and water quality crashes.
According to the University of Minnesota Extension, fish in outdoor ponds “enter a state of torpor where feeding is unnecessary and even harmful” during cold months (UMN Extension, 2022). One of the biggest mistakes pond owners make is feeding “because the fish look hungry.” In reality, koi and goldfish are opportunistic eaters—they’ll nibble at food out of instinct even when their bodies can’t digest it. That uneaten or undigested food becomes rot in their stomachs and sludge at the bottom of the pond, compounding oxygen loss over winter (and possibly the death of your fish). Cutting off feeding isn’t starving your fish—it’s saving them.
3. Draining & Capping Plumbing
Your pump and plumbing aren’t built for sitting idle during Minnesota’s freeze-thaw cycle. As water freezes, it expands, cracking pipes, filters, and biofalls. That’s why proper shutdown is essential.
Steps include:
- Turn off your pump and drain biofalls and waterfall systems.
- Flush plumbing lines and cap them for winter.
- Store pumps indoors (older pumps in a bucket of water to keep seals lubricated).
Aquascape’s Seasonal Maintenance Guide emphasizes that “equipment longevity depends on proper winter storage—pumps left outside risk permanent damage.” Plumbing failures are among the costliest winter damages. A cracked biofalls or skimmer housing can easily run into thousands of dollars in replacements come spring. Properly draining and capping your plumbing not only prevents expensive damage, it also saves time—ensuring your startup in Spring is smooth instead of starting with a repair bill.
4. Aerators & Deicers: Keeping Fish Alive
Even in dormancy, your fish need oxygen and a way for gases to escape. Ice-covered ponds trap harmful gases like carbon dioxide and methane. The solution: a winter aerator and pond de-icer to maintain a small open hole.
- Aerators circulate water and keep oxygen levels stable.
- Deicers gently warm a small hole in the ice to prevent full freeze-over.
The U.S. Geological Survey notes that “oxygen depletion under ice cover is one of the primary causes of winter fish kills in northern ponds” (USGS, 2021). The size of your pond determines what you need. While smaller ponds down in southern Minnesota like Rochester, Owatonna, and Mankato areas may only require a single aerator, larger ponds just south of the cities and up typically require both an aerator and deicer working together. Aerators alone won’t keep a hole open during extreme cold snaps, and deicers without aeration do not provide enough oxygen circulation. A balanced system ensures that your pond survives even the harshest Minnesota winters and that healthy sludge breakdown is occurring.
5. Never Break Ice by Force
As many pond owners have unfortunately learned, smashing ice is dangerous. The shockwaves can kill fish already stressed by winter. Instead, rely on your aerator or deicer to keep water breathable. If you must create an opening, pour a pot of hot water over the surface instead of hammering.
Beyond the risk to your fish, breaking ice is also a hazard for you. Slipping on frozen surfaces or accidentally cracking frozen equipment are common accidents we see homeowners run into. Safe winter pond care isn’t just about your ecosystem, it’s about protecting you too. A few minutes with the right equipment saves hours of stress and risk all winter long.
Why This Is Different in Minnesota
Pond prep advice from warmer regions won’t cut it here. Our freeze-thaw cycles stress liners, fittings, and equipment more than in milder states. What works in California or Missouri can fail quickly in the Twin Cities. By following Minnesota-specific steps, you’re not just “winterizing,” you’re preventing expensive repairs and rebuilds and protecting your fish and ecosystem long-term.
Learn more about essential winter fish prep in our winter fish care guide.
Summary & Takeaway
Minnesota pond owners face unique challenges each fall and winter. But with:
- Netting for debris,
- Smart fish feeding,
- Proper plumbing shutdown,
- Aerators & deicers, and
- Avoiding ice-breaking…
…you can keep your pond safe and your fish healthy until spring!
How Superior Ponds Can Help
While some pond owners take on winter prep themselves, many prefer the peace of mind that comes with having a professional handle it. At Superior Ponds, we offer full-service fall netting and winter shutdowns, making sure every detail is covered. From stretching netting at the right time, to safely draining and capping your plumbing, to installing aerators and de-icers so your fish stay safe all winter long. Best of all, you can explore pricing for these services ahead of time using our free online estimator, giving you transparency and confidence before you ever book!
When you’re ready to book for Fall and Winter, give us a call to get started!