Fall, when pumpkin spice arrives, leaves turn golden, and your koi start acting like sleepy little water balloons. As temperatures drop, your pond begins its annual shift from summer madness to winter calm, and your koi need your help to make that transition smooth, safe, and drama-free.
Fall is one of the most important seasons for koi keepers. Do it right, and your koi enter winter strong, healthy, and ready to wake up beautifully in spring. Do it wrong, and winter becomes a months-long nail-biter filled with cold-weather surprises.
Let’s walk through an entertaining yet essential guide to preparing your pond (and your koi) for cooler weather.
1. Watch the Temperature—Not the Calendar
Koi don’t care about the date—they care about water temperature. Fall pond prep begins when temps dip consistently below 70°F (21°C) and continues until they approach winter levels.
Why temperature matters:
- Koi metabolism slows as water cools.
- Beneficial bacteria become less active.
- Parasites love the in-between temperatures (the freeloaders!).
Tip: Keep a pond thermometer on hand. It’s more useful than any weather app.
2. Adjust Feeding Before Your Koi Adjust Themselves
Fall feeding is all about preparing koi for the long winter fast. This means wheat germ food becomes the star of the season.
Fall Feeding Rules:
- 65–70°F: Begin mixing in wheat germ pellets.
- 55–65°F: Feed only wheat germ, small amounts.
- 50–55°F: Reduce feeding significantly.
- Below 50°F (10°C): Stop feeding completely.
Koi may act hungry under 50°F, but their digestive systems are basically in hibernation. Feeding them below that temp is like handing someone a steak while they’re sleepwalking—not ideal.
3. Clean the Pond Before Winter Makes It Hard
Winter locks debris in place like nature’s freezer. If you don’t clean now, you’ll have a sludge party in spring—and nobody wants that.
Key fall cleaning tasks:
- Remove fallen leaves before they rot.
- Trim back plants, especially lilies and marginals.
- Scoop sludge from the bottom if needed.
- Check and empty skimmer baskets daily during heavy leaf fall.
A clean pond equals healthier water and far fewer wintertime headaches.
4. Install a Leaf Net (Your Future Self Will Thank You)
A leaf net is one of those pond accessories that makes you wonder why you didn’t buy it years ago. It prevents leaves from sinking, rotting, and creating toxic soup under the ice.
Plus, it saves your pumps and skimmers from being smothered by a sudden leaf avalanche.
Tip: Install it early—leaves fall fast, and koi are notoriously bad at cleaning up after themselves.
5. Deep-Clean Your Filtration (But Don’t Kill the Bacteria!)
Your filtration system has been working overtime all summer. Give it a fall tune-up so it can handle the slow season ahead.
Do:
- Rinse mechanical filter pads gently with pond water.
- Clear out settlement chambers or sieves.
- Check pumps for wear or blockages.
- Ensure pipework and hoses are secure.
Don’t:
- Wash bio-media with tap water (chlorine will murder your beneficial bacteria).
- Turn off filtration too early—the bacteria still need time to adjust.
Fall filtration mantra: Clean, but not too clean.
6. Check Oxygen Levels as Plants Slow Down
Plants and algae produce oxygen during the day but consume it at night. As fall cools the water and sunlight fades, oxygen levels shift.
Increase or maintain oxygen by:
- Running air stones through fall and winter.
- Keeping waterfalls active as long as temps allow.
- Clearing excess plant matter.
Proper oxygenation helps koi stay strong and stress-free as their metabolism slows.
7. Monitor Water Quality Closely
Fall is notorious for surprise ammonia spikes because:
- Filters slow down.
- Plants die back.
- Leaves decay.
- Koi still produce waste.
Test weekly for:
- Ammonia
- Nitrite
- Nitrate
- pH
- KH
Stable water quality now leads to a healthier winter — and avoids spring disasters.
8. Consider a Pre-Winter Salt Level
A low salt level (0.05–0.1%) can help koi transition into colder weather by supporting the slime coat and reducing stress.
Just don’t go higher unless treating a problem — this is a seasonal boost, not a salt bath.
9. Start Planning for Winter Equipment
Fall is the time to prep your winter gear:
- Pond heater or de-icer
- Backup aeration system
- Winter covers or greenhouse-style tents
- Spare pumps (just in case)
Being prepared now means you won’t be outside in December with frozen hair trying to thaw a clogged skimmer.
10. Observe Your Koi Daily
Fall is a sensitive season—parasites and bacteria are active, but koi immune systems are slowing down. Keep an eye out for:
- Clamped fins
- Listlessness
- Flashing
- Red streaks in fins
- Visible sores
If you spot problems early, you can treat before winter shuts down your options.
Fall pond preparation isn’t just about getting ready for winter—it’s about giving your koi the best chance for a healthy, stress-free cold season and a strong spring comeback.
Clean smart, feed wisely, test regularly, increase oxygen, and prepare ahead. Do these simple steps, and your koi will drift into winter as happy, plump, and peaceful as floating autumn leaves.
Fall may be the season of change—but with the right preparation, it’s also the season of future pond success.