Winter is finally loosening its icy grip, the sun is showing its face again, and your koi are slowly emerging from their chilly, slow-motion slumber. It’s officially spring start-up season — that magical time when ponds come alive, filters restart, and koi begin acting like they haven’t eaten since 1994.
But hold on! Before you grab the food bucket and start tossing pellets like confetti, there’s a right (and safe) way to wake your pond after winter. Spring is one of the riskiest times for koi; their immune systems are sluggish, parasites wake up faster than they do, and water quality can get weird.
Let’s walk through a fun and effective spring start-up routine to make sure your koi transition from winter hibernation to summertime glory without a hitch.
1. Start With a Visual Pond Inspection
Before you touch a filter or plug anything in, give your pond a slow, thoughtful look. Pretend you’re an aquatic detective.
Check for:
- Ice damage around edges or skimmers
- Sticks, leaves, or accumulated winter sludge
- Any dead plant material floating around
- Leaks or lowered water level
If your pond looks like a swampy salad, don’t worry—we’ll fix that in a minute.
2. Clean Out Winter Debris (Gently!)
Winter dumps all kinds of junk into ponds—leaves, twigs, mystery sludge, maybe even a stray mitten or two. Removing debris now prevents ammonia spikes and gives your koi a clean slate.
To clean safely:
- Use a pond net to scoop surface debris.
- Vacuum the bottom if needed—but avoid disturbing koi too much.
- Remove dead plants; trim living ones.
Important: Don’t drain the whole pond unless it’s part of your normal maintenance. A sudden 100% water change is like dropping your koi into a new planet.
3. Test Your Water Before Restarting Feeding
Winter can play tricks on your water chemistry. Fish barely eat, beneficial bacteria slow down, and pH and KH may shift.
Test now for:
- Ammonia
- Nitrite
- Nitrate
- pH
- KH
- Temperature
If ammonia or nitrite is above zero, you’ll want to address that before feeding your koi—or their breakfast becomes a biochemical time bomb.
4. Restart Your Filtration System
This is the moment your pond starts waking up for real. But do it carefully.
Steps for a smooth restart:
- Clean mechanical filter pads gently with pond water (never tap water!).
- Check pumps and lines for cracks or blockages.
- Restart the pump and waterfall.
- Monitor for leaks.
- Add beneficial bacteria to help jumpstart the biofilter.
Your biofilter is like a sleepy bear waking from hibernation—it needs time and snacks (ammonia) to get going again.
5. Gradually Increase Aeration
Cold water holds more oxygen, so koi do fine with less aeration in winter. But spring warming can quickly lower oxygen levels.
Make sure:
- Air stones are working.
- Waterfalls are flowing.
- There’s good surface movement.
Your koi are about to become much more active—they’ll appreciate the extra O2.
6. When to Start Feeding (And When NOT To)
This is the question every koi keeper debates at the first warm day of spring:
“Can I feed them yet?”
The answer depends on your water temperature, not your koi’s begging skills.
- Below 50°F (10°C): No food. Their digestion is basically off.
- 50–55°F (10–13°C): Small amounts of wheat germ food only.
- 55–60°F (13–15°C): Increase feeding slowly.
- Above 60°F (15°C): Normal feeding resumes.
Fun fact: Koi will try to convince you they’re starving at any temperature. Don’t fall for it.
7. Watch Out for “Spring Parasite Season”
Spring is prime time for parasites—flukes, Costia, and Ich love the warmer water. Meanwhile your koi’s immune system is waking up sloooowly.
Keep an eye out for:
- Flashing (scratching)
- Clamped fins
- Lethargy
- Red streaks in fins
- Cloudy skin or excess slime
If you see these early, you can treat in quarantine before it spreads.
8. Perform a Partial Water Change
Fresh water is like a reset button for your pond. A good spring water change helps dilute winter’s buildup and stabilizes your parameters.
Do this safely:
- Change 10–20% of the water.
- Match temperature as closely as possible.
- Always add dechlorinator for tap water.
Cold “shocking” your koi in spring is extremely stressful—even more than waking up early on a Monday.
9. Inspect Your Koi Up Close
Spring is a perfect time to look at each fish’s body condition.
Check for:
- Ulcers or red patches
- Frayed fins
- White spots
- Raised scales
- Weight loss from winter
Catch problems now, while they’re small.
10. Consider Adding Seasonal Supplements
Optional but helpful:
- Beneficial bacteria (to jumpstart the filter)
- Low-level salt (0.05–0.1% to reduce stress)
- Clay minerals (improves water clarity and koi color)
Just don’t go overboard—spring is about balance, not chemical soup.
Spring start-up is one of the most important times of year for koi keepers. When done right, it sets the stage for healthy growth, vibrant colors, and a stress-free season.
Clean gently, test carefully, restart slowly, feed wisely, and observe constantly. Your koi will reward you with joyful swimming, bright colors, and endless entertainment all summer long.
Welcome back to pond season — let the koi fun begin!