How to Feed Adult Koi Fish

Updated on July 1, 2019
Jana Louise Smit profile image

Jana worked in animal welfare with abused and unwanted pets. She loves sharing her hands-on experience regarding domestic and wild critters.


What You'll Learn About Koi

  • What koi need to eat
  • How to pick the best commercial foods
  • Why some ingredients are essential
  • When to give fresh foods and supplements
  • Seasonal feeding needs
  • Feeding; how often and the amounts

Koi Love to Eat

Your pet fish adores anything that hits the surface of its pond. For this reason, koi often eat things that are not nutritious, or they overeat. It's your job to make sure that this hearty appetite is met with a balanced diet. Here's the good news: koi feeding needn't be complicated. High-quality commercial food is quite sufficient. However, variety is key. You can give commercial food, treats, and occasional live foods to keep things yummy in your koi's tummy.

Pick the Best Commercial Food

Unfortunately, when it comes to your koi's dinner, price determines quality. A cheap brand would likely not provide all the necessary nutritional benefits that are required. The product must also have the right size pellets suitable to your pet's age and constitute a complete diet. The latter should include ingredients derived from both animal and plant sources, as well as vitamins, minerals, fat and protein.

The Importance of Protein

Without protein, koi won't grow or be able to heal themselves. They'd have no energy. In short, protein is essential to their survival. Youngsters under the age of three also need more, between 30 and 36 percent of their total diet. The elders of the clan may enjoy the same levels during summer, but lower the amount to 25 percent through fall and winter when colder weather makes their digestive system slow down. Fish in warmer areas can stay on the protein scale's high end no matter the time of year.

Additional Essential Ingredients

  • Carbohydrates. The dietary percentage of this quick energy source should not surpass 70 percent (too much can lead to overweight koi).
  • Oils and fats, otherwise known as lipids. A good source of energy and vitamins, fat should make up 3 to 10 percent of their diet; juveniles start at 10, then go lower down the scale as they mature into adults.
  • Vitamins and minerals. The exact requirements for koi remains debatable, but it's a good move to purchase food from trusted, long-established brands.
  • Fiber. Commercial products should show around 5 percent inclusion of fiber.

Overfeeding Ruins Water Quality

Koi that are overfed not only produce more waste, but also ignore food that ends up spoiling.
Koi that are overfed not only produce more waste, but also ignore food that ends up spoiling. | Source

Floating and Sinking Foods

Commercial feeds are designed to either sink or bob at the surface. Floating food brings koi to the surface where their beauty can be appreciated and their health assessed. Fry also instinctively gobble up bits drifting on the surface. Drifting pellets also allow you to see how much food remains uneaten. Sinking pellets are better for the cooler seasons when koi are less active and not as hungry.


Koi may snack in moderation. It provides variety for them and enjoyment for the owner. Who doesn't love spoiling a pet with a tasty treat? Consider some of the following spring and summer treats.

  • Oranges. Keeping the skin intact, divide the orange into six pieces, or slice the fruit into wheels. Koi love picking at the pulp.
  • Romaine lettuce. Take one head and cut into quarters. Koi take longer to eat this snack, but it will eventually be shredded and consumed.
  • Live foods like earthworms, crayfish and freshwater glass shrimp. Toss a few into the pond, but don't overfeed.
  • Avoid giving white bread and rice; koi may love them, but they are nutritionally worthless.

Professional Beggars

Koi learn to recognize their keepers and will wait for you at its feeding station when it's meal time.
Koi learn to recognize their keepers and will wait for you at its feeding station when it's meal time. | Source

The Need for Supplements

When a diet is well-balanced, supplements aren't really necessary. Koi get all their nutritional needs from good commercial food and live snacks. However, some breeders add extras to help fry grow and to enhance colour. The latter is achieved by using products containing spirulina or carotene. Should you opt for a colour supplement, make sure you read the directions and feed it to the right fish. Enhancers tend to infuse white skin with pink, a devastating change to high-grade show fish requiring a porcelain look. Colour supplements are also used during certain times of the year when the water is not too cold. Check the label or do your research before choosing this route.

Seasonal Feeding

Correct feeding is tied to temperature, both seasonal and day-to-day. It's essential your thermometer delivers accurate readings from the bottom of the pond. This is more important than air temperature.

  • 50 degrees (or below) Fahrenheit. Don't feed. Koi usually won't eat when it's this cold, neither can they digest their food
  • 50–55 degrees. Wheat germ pellets, once a day
  • 55–70 degrees. Wheat germ pellets twice a day
  • 70–75 degrees. Floating pellets up to four times a day. If cold weather or seasons are approaching, condition your koi with additional bi-weekly treats (live foods)
  • 75 degrees and higher. Floating pellets up to four times a day.

Feeding: How Much and When

Pond water quality suffers when overfed fish excrete more waste, or when uneaten food decomposes. A solid rule is to throw some pellets and wait 5 minutes. Should your koi eat everything before the time's up, toss additional pellets and wait another 5 minutes. This eventually gives you an idea of the quantity they can consume within 5 minutes.

Koi don't mind when they are fed, but it's best to keep them on a schedule. You'll be amazed at how quickly koi learn their feeding times! As the hour draws near, they'll gather near the surface or the spot you usually stand while dispersing food. As a rule, any time during the day is fine. Choose whenever suits you, but keep the time slots dispersed so that they won't go hungry.

Questions & Answers

  • I've got quite a large Angel koi that has a "ballast" problem. It can't keep a horizontal position. What should I do to help correct this?

    If your fish swims normally but fails to hold an upright position now and again, you may need to check your water conditions. Sometimes too much ammonia in the pond or tank can affect their ability to swim normally. However, when your koi display this "ballast" behavior permanently, then you may be looking at a problem with the swim bladder.

    Treatment for bladder problems can be successful. There are several remedies out there. Please do proper research on the internet and see which one works for you at home. You can always contact a koi expert or vet specializing in aquarium pets. Should you choose a home treatment, make certain that the source or web site is one that deals expertly with koi problems.

© 2018 Jana Louise Smit


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