At SJ Koi Carp in Kent, we know how much passion and care goes into keeping koi healthy and happy. These beautiful fish thrive in well-balanced, well-maintained ponds, but as UK summers become warmer and more unpredictable, it’s more important than ever to take steps to protect them during the hotter months.
Whether you’re a new koi keeper or have years of experience, it’s always worth reviewing how to support your pond life when temperatures climb. Here’s our guide to keeping your koi cool, comfortable and safe all summer long.
Why Summer Poses a Challenge for Koi
While koi can adapt to a range of temperatures, extreme or sustained heat can cause stress, reduce oxygen levels in your pond and increase the risk of disease. Warm water also accelerates the metabolism of koi, meaning they eat more and produce more waste, which can unbalance your pond ecosystem if you’re not prepared.
Add to that the effect of intense sunlight encouraging algae blooms and it’s clear summer takes a bit of extra effort.
1. Maintain Ideal Water Temperature
Koi prefer water between 15°C and 25°C. Once temperatures rise above 25°C, you may start to notice signs of stress, especially if oxygen levels are low.
To help regulate temperature:
- Add shade. Use pond plants like lilies or float covers to reduce the amount of direct sunlight hitting the water.
- Install a pergola or sail over part of the pond to provide long-lasting shade.
- Avoid black pond liners in exposed areas, as they absorb and trap heat.
2. Keep Oxygen Levels High
Warm water holds less oxygen, and your koi need more of it in the heat. It’s a tricky balance, but there are simple ways to give your pond a boost.
- Add or upgrade an air pump. A good air pump with air stones placed around the pond will help oxygenate the water effectively.
- Use a water feature like a waterfall, fountain or venturi to keep water moving and oxygen-rich. At SJ Koi Carp, we supply and build custom features that look good and serve a real purpose.
- Avoid overstocking during summer, as more fish means greater oxygen demand.
Watch for signs of low oxygen such as koi gasping at the surface or clustering near inflow areas.
3. Control Algae Growth
Algae thrive in sunny, warm conditions. Green water and blanketweed are the most common issues and both reduce water quality.
To stay on top of algae:
- Limit excess nutrients by not overfeeding and by cleaning filters regularly.
- Use UV clarifiers to keep green water under control.
- Consider barley straw or dedicated algae treatments – we stock several options and are happy to advise which suits your pond best.
Consistent maintenance and the right equipment go a long way in keeping algae at bay.
4. Monitor Water Quality Closely
Summer is not the time to let testing slide. Increased feeding and biological activity can quickly lead to imbalances.
Test for:
- Ammonia
- Nitrite and nitrate
- pH
- Oxygen levels
- Temperature
Use a good-quality water test kit weekly during the hotter months. If anything looks off, act quickly. At our shop in Kent, we stock reliable test kits and can talk you through how to use them if you’re unsure.
5. Adjust Feeding Habits
Your koi will be more active and hungrier in warm weather, but overfeeding can pollute your pond and strain your filtration system.
Stick to these feeding tips:
- Feed little and often, and only what they can eat in a few minutes.
- Use summer-grade koi food with higher protein to match their increased activity. We have a full range of seasonal koi foods available.
- Avoid feeding during the hottest part of the day when oxygen levels are at their lowest.
A good diet, matched to the season, helps your koi grow well and stay strong.
6. Keep an Eye Out for Health Issues
With stress levels rising in warmer temperatures, koi are more vulnerable to parasites, bacterial infections and wounds. Check your fish daily if you can.
Look out for:
- Flicking or rubbing against surfaces
- Lethargy
- Unusual swimming behaviour
- Red patches, ulcers or visible parasites
We offer water testing, microscope diagnostics and health treatments in store. If you’re concerned about your koi, pop in or give us a call for guidance.
7. Prepare for Power Cuts or Equipment Failure
Summer thunderstorms can knock out power and filters unexpectedly. It’s always worth having a backup plan.
We recommend:
- Battery-powered air pumps or generators if you’re in a rural area
- Spare parts for pumps or filters so you’re not stuck if something fails
- Regular maintenance of all pond equipment
We can advise on what backup kit might suit your setup, whether it’s a small garden pond or a larger feature.
Visit SJ Koi Carp for All Your Summer Pond Needs
Here at SJ Koi Carp in Kent, we love helping pond owners get the best out of their setups. Whether you need new filters, top-quality food, expert advice or a full water feature build, we’ve got the experience and the stock to support you through the hottest days of the year.
Our team includes koi experts and pond construction professionals, and our shop is fully stocked with everything from pumps to treatments. We’re happy to talk through your pond setup and help you plan for a smooth, safe summer.
