Choosing Food For Your Koi

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Oh, my aching muscles...

By Diahan Krahulek

Seeing your carefully planned water garden bloom into hundreds of colors and textures throughout the season is, no doubt, extremely rewarding. Flowers and plants require cultivation to reach their potential, and the results validate your hard work. However, don’t forget that your Koi also need “cultivating” to maximize their vibrant colors, growth, and longevity.

Koi are omnivorous opportunistic feeders—meaning they need both protein and plant matter in their diets and will look for these nutrients anywhere they can get them. It’s fun to watch Koi scramble to eat bread crumbs or Cheerios, but depriving them of a balanced diet created for their physiological needs affects their color and energy level and decreases their ability to fight disease. Choosing quality Koi foods and learning how much and when to feed them are critical elements in maintaining your pond.

Koi are naturally bottom feeders because of the shape of their mouths, but there are several reasons why it is best to use floating foods. Bringing your fish to the surface allows you not only to enjoy their beauty but also to check for injuries and overall health. Over time, your fish will recognize you as their food source instead of a predator and will spend more time in view when you are around.

Buying Koi flakes, pellets, or sticks is not as critical as making sure the consistency of the food allows for easy digestibility. Since Koi do not have teeth or stomachs, they are unable to break down food in the same way we do by chewing and with acid digestion. Anything they cannot process is excreted back into the pond, increasing your chance of algae blooms. Choose a floating food that is not too dense but does not break apart when thrown into the pond. Water should soften food just enough to allow the fish to break it down with the pharyngeal bones in the back of their mouths before passing it through their intestines.

Healthy Koi require the proper amounts of proteins (amino acids), fats (lipids), carbohydrates, vitamins, and minerals. Proteins increase growth and reproduction, and fats give fish energy. Look for 31 to 42 percent crude protein and two to three percent crude fat on the nutrition analysis panel. While carbohydrates offer an energy boost, their main purpose is to help fish process food nutrients, and vitamins and minerals regulate their metabolisms. Using manufactured maintenance foods offsets what fish would normally scavenge in the wild but are unable to get in backyard ponds.

Because fish meal provides the bulk of protein in fish diets and is easier to digest than most grain proteins, it should be listed as one of the leading ingredients for staple foods. Ground corn is often considered filler; however, corn gluten and flour have been tested to be highly digestible and provide needed nutrients and vitamins. Koi also need Vitamin C to develop their immune systems so make sure foods include ascorbic acid.

While synthetic ingredients in human food continues to be debated, this issue is not so critical for Koi food since fish process synthetic and natural ingredients in the same way. Natural ingredients are preferred, of course, but food manufacturers may need to use synthetic ingredients to ensure the fish receive balanced diets based on their natural environments. 

Seasons and water temperatures affect the type, amount, and frequency of Koi food to use. During the warmest part of the pond season, when water temperatures are higher than 70 degrees, fish digest their food in four to five hours which is why feeding staple foods three to four times per day—and only as much as they can eat in about five minutes—is recommended. To reduce maintenance and potential problems with water quality, be sure to remove any uneaten food with a net before it sinks to the bottom. If you want to enhance the reds of your Koi, alternate feeding a staple diet with color-enhancing foods that contain spirulina, shrimp, or krill every four weeks. This method improves color without turning the white parts of your fish pink.

Add some more variety by feeding live foods. Koi naturally eat crustaceans, insect larvae, worms, and aquatic plants in the wild. Live plants offer fish roughage and some necessary vitamins and minerals. Just remember that these supplemental foods should complement Koi diets but never replace nutritionally balanced staple or maintenance foods.

Once water temperatures are consistently above 60 degrees in the spring, start feeding your fish wheat germ sticks. At 70 degrees and above, switch to staple foods. For a couple of weeks at this point, you may want to start out with Koi growth foods that contain higher protein and fat levels. Not only do these foods help younger fish grow quicker but also help established fish combat low energy reserves from not eating all winter.

In the fall, just follow the spring feeding schedule in reverse. Besides watching your pond thermometer, you will know to make the change when your fish start spending more time near the bottom of your pond where it is warmer. As temperatures get lower for the winter, so do Koi metabolisms. Transition Koi to a lighter diet by mixing wheat germ sticks or pellets to regular Koi staple foods or purchasing blended diets that already include wheat germ sticks. Once temperatures fall below 60 degrees, switch completely to the wheat germ diet, and, below 50 degrees, stop feeding the fish altogether for the entire winter to avoid food decaying in their systems.

Store foods in airtight plastic containers to avoid moisture and in a cool, dry place away from sunlight. Koi food loses its nutritional effectiveness if kept too long and even faster if exposed to sunlight and heat regularly.

Ultimately, choosing the right Koi food keeps your fish and your pond ecosystem healthy and allows your filtration system to work efficiently and maintain clear water. If you spend a little more money up front for quality food, you will save on maintenance time and costs throughout the season.


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