Philadelphia summers don't mess around. When the humidity settles in and the temperature climbs into the 90s, your koi feel it just as much as you do — they just can't tell you about it.
Here's the thing that catches people off guard: warm water holds less oxygen. The hotter your pond gets, the less air is dissolved in it, right when your fish are most active and need it most. That's the heart of summer koi care.
Keep the oxygen up
Moving water is oxygenated water. Make sure your waterfall, stream, or fountain is running strong through the hot stretch — this isn't the season to shut it off. Adding an aerator gives you a real cushion on the worst days. If you ever see koi hanging at the surface gulping air in the early morning, that's a low-oxygen warning, and it's time to act.
Throw some shade
A little shade keeps water temperatures in check and slows down algae. Water lilies and floating plants are perfect for this — cover a good chunk of the surface and your fish get cooler water and hiding spots at the same time. Deeper ponds ride out heat better too, since the bottom stays cooler than the top.
Rethink feeding
Koi metabolisms run fast in warm water, but their oxygen supply is tight, and digestion uses oxygen. Feed in the cooler hours of the day — early morning or evening — and don't overdo it. On the most brutal days, easing off the food gives their systems a break.
A few quick things to watch for when it's hot:
- Fish gasping at the surface, especially at dawn
- Water level dropping faster than usual from evaporation
- Sudden algae blooms turning the water green
None of it is hard once you know what you're looking at. Keep the water moving, keep it shaded, feed smart, and your koi will cruise through the worst of a Philly summer.
If your pond struggles every time it gets hot, something in the setup may need tuning. Call us at 215-880-6811 or get in touch and we'll help you get ahead of it before the next heat wave.