Summer—the season of sunshine, BBQs, iced tea, and koi acting like energetic underwater puppies. Warm weather brings out the best in your pond… and the worst if you’re not prepared. High temperatures, booming metabolism, and explosive algae growth can turn a dream pond into a bubbling cauldron of chaos if you don’t stay ahead of the game.
But fear not! With the right summer care routine, your koi will glide through the warm months like the majestic, pampered water dragons they are. Let’s dive into the essential summertime secrets of oxygen, feeding, and filtration.
1. Oxygen: Your Pond’s Lifeline (Especially in Summer)
Warm water is wonderful for koi activity—but terrible for oxygen levels. As temperatures rise, dissolved oxygen levels drop. Combine this with hungrier koi, active bacteria, and nighttime plant respiration, and suddenly your fish are gasping like joggers running uphill with soda lungs.
Signs Your Pond Needs More Oxygen:
- Koi hanging at the surface or near waterfalls
- Heavy gill movement even while resting
- Jumping or gulping at the surface
- Sluggish behavior during the hottest parts of the day
Easy Ways to Boost Summer Oxygen:
- Add extra air stones or increase air pump capacity.
- Run waterfalls and fountains 24/7.
- Aim return jets upward to agitate the surface.
- Thin out excessive plant or algae growth.
- Keep filters clean for optimal flow.
Pro tip: Oxygen levels are lowest just before sunrise. If koi act weird in the early morning, oxygen is probably the culprit.
2. Feeding: High Energy, High Stakes
Summer is the koi equivalent of Black Friday—their metabolism skyrockets, and they’re ready to eat everything that hits the surface. But more food = more waste = more ammonia = more filtration stress.
Summer Feeding Rules:
- Water above 70°F: multiple small feedings per day (not one giant dump).
- Use high-protein foods: 35–40% protein supports growth and energy.
- Supplement with treats: watermelon, orange slices, peas, shrimp.
- Remove uneaten food within 5 minutes.
- Don’t feed during heat spikes or storms.
Koi lie. They will act like they’re starving even if you fed them five minutes ago. Don’t fall for their adorable aquatic manipulation.
What NOT to Feed in Summer:
- Starchy winter foods
- Bread (ever!)
- Old, expired pellets
- Large clumps of food that sink fast
Bonus tip: Feed earlier in the day. It's cooler, oxygen is better, and digestion is smoother.
3. Filtration: The Unsung Hero of Summer
Your filter works hard all year, but in summer it becomes the pond’s version of a busy restaurant kitchen—nonstop action. More feeding, more fish activity, and faster metabolism all produce extra waste. If your filtration is even slightly underpowered, summer will reveal it.
Keep Your Filtration System Happy:
- Rinse mechanical filter pads weekly with pond water.
- Flush settlement chambers or sieve trays often.
- Check skimmers for plant clogs and leaves.
- Ensure biofilters have strong aeration.
- Top off water levels to maintain flow.
Never clean bio-media with tap water! That’s like firing your entire beneficial bacteria staff in one day.
Is Your Filtration Big Enough?
If your water gets cloudy, green, or smelly in summer, your filtration might be undersized. Upgrading may include:
- Adding a moving bed filter
- Upgrading pump size
- Installing a UV sterilizer
- Adding a sieve or drum filter
Big koi produce big waste. Your filter must match their enthusiasm.
4. Managing Algae: The Summer Trouble-Maker
Sun + nutrients = algae throwing a rave in your pond. Green water and string algae can appear almost overnight in the summer heat.
Tips to Keep Algae Under Control:
- Use a strong UV clarifier for green water.
- Keep nitrates low through water changes.
- Add shade—plants, shade sails, or floating lilies.
- Don’t overfeed (algae love leftovers).
- Maintain a healthy biofilter (starves algae of nutrients).
Fun fact: Some algae is actually beneficial. It absorbs ammonia and provides oxygen—but too much can suffocate fish.
5. Water Changes and Evaporation Control
Summer heat evaporates water quickly, leaving your pond low and your pump at risk.
Do this regularly:
- Top off evaporated water weekly.
- Add dechlorinator EVERY time (tap water contains chlorine/chloramine!).
- Perform 10–20% water changes to keep nitrates in check.
Never let your pump suck air. That’s how pumps die… dramatically.
6. Watch for Summer Stress and Illness
Summer warmth wakes up both koi and parasites. Keep a close eye on behavior:
- Flashing or rubbing = parasites
- Gasping = oxygen problem
- Lethargy = water quality or temperature
- Red fins = stress or ammonia
Catching problems early is your superpower.
Summer is the season your koi live their best lives—fast growth, bright colors, endless activity. But it’s also the season where ponds require the most attention.
Keep the water oxygen-rich, feed smartly, maintain strong filtration, and stay ahead of algae and heat stress. With these simple habits, your koi will glide through summer like sparkling underwater torpedoes.
Happy summer—and happy koi keeping!