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Could Your Koi Have a Sunburn?

Could Your Koi Have a Sunburn?

Sunshine has its benefits - but it also has its dangers. Direct sunlight with no shade can raise the water temperature in your pond and reduce the levels of oxygen available to your fish. All those rays can also fuel algae blooms, as well as give your fish a sunburn (yes, really!).

As it turns out, Koi fish in backyard ponds and water gardens are particularly susceptible to sunburn. Combine a shallow body of water, limited shade, and long hours of hot, summer sun, and Koi fish suffer from the aquatic equivalent of sunburn.

Like all other fish, Koi fish rely on a natural protective layer - otherwise known as a "slime coat" - that fends off everything from disease to injury. When Koi fish are exposed to too much direct sunlight, their slime coats are compromised, and sickness and lethargy follow quickly. Left unresolved, long-term exposure to sunlight will actually cause a Koi's untimely demise. Fortunately, it's a simple problem to fix - and we have the right supplies to do it.

  • Terrestrial Shade: Trees, and terrestrial and marginal plants growing alongside your pond can provide plenty of shade from the outside. Blue Flag Iris and Dwarf Cattail, for instance, planted on the south or west side will cast cool, shady shadows for your fish.
  • Get Creative with Canopies: If planting trees or plants isn't an option, consider installing a tent or canopy over part of your pond. In addition to creating protection from the sunshine, a canopy can also add some dramatic flair to your backyard décor.
  • Floating Plants: Floating aquatic plants, like water lilies and water hyacinth, create scads of underwater shade for your finned pals. Simply plant lilies in baskets or plant bags and place them in strategic spots around your pond or toss in water hyacinth to create a floating hideout.
  • Fish Shelters: For a super easy solution, drop some fish shelters, like the Nycon Koi Kastle Fish Shelter, in your water garden. Another option is to create fish caves with carefully positioned rocks. They'll create a shady shelter that'll protect the fish from sun - and predators.
  • A word of advice: Don't over shade your pond. You still want to maintain an area with some sunlight, which helps bring out koi colors, keep the water a comfortable temperature and help your plants grow.

    If you think your fish are already showing signs of heat stress, check your water temperature with a pond thermometer, and do a partial water change if the water temperatures reach the high 70s or above. You might also want to add some pond salt, which will help gill function and reduce fish stress, as well as some Stress Reducer Plus, which alleviates stress, restores their slime coat and removes dangerous toxins from the water.