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Learn the nutritional needs of these popular pond pets.
By Julie Mancini
I’ll admit it — my weakness for feeding koi started when I first fed the fish in the koi ponds at Kelley Park’s Japanese Friendship Garden in San Jose, Calif., about 10 years ago. The scene was so tranquil and relaxing, I quickly was hooked on the appeal of feeding koi.
The tranquility and relaxation tempt many pond keepers to add koi to their water gardens. When feeding koi in your pond, select a well-balanced koi diet and supplement it with some fresh foods. By providing small meals throughout the day and promptly removing leftovers, you can keep your koi well-fed and happy with minimal effort.
NUTRITION REQUIREMENTS
Koi need five important nutrients for energy, growth, proper food utilization and organ function, said long-time koi keeper Chris Neaves, who created Associated Koi Clubs of America’s nutrition education program. Those nutrients include amino acids (protein), lipids (fat), carbohydrates, vitamins and minerals.
Amino acids help koi grow, reproduce and maintain good health. Neaves said koi need 10 amino acids — arginine, phenylalanine, histidine, isoleucine, leucine, lysine, methionine, threonine, tryptophan and valine — supplied to them via their diets because their bodies cannot make them naturally.
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Fresh Foods to Feed Your Koi
Koi keepers can offer their fish a variety of fresh foods to provide important vitamins and other nutrients and to supplement standard koi diets. Your fish might enjoy these foods:
Fruits: strawberries, blueberries, oranges, lemons, grapefruit, watermelon, apples
Vegetables: squash, peas, cucumber, carrots, tomatoes, kale, green pepper, romaine lettuce, Boston lettuce (Note: Iceberg lettuce contains few nutrients for koi.)
Breads and cereals: brown bread, wheat germ, unsweetened cereals such as Cheerios, oatmeal
Greens: alfalfa, duckweed, fairy moss, water celery, dandelion greens, water hyacinths
Protein: worms, prawns, tadpoles, brine shrimp, daphnia, silkworm pupae, organ meats such as kidneys or liver, beans. – J.M.
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Lipids are the most concentrated form of energy in koi diets. Lipids help supply a koi’s energy needs, according to Neaves. They also carry fat-soluble vitamins such as A, D, E and K through a koi’s body.
Carbohydrates help a koi’s body process the nutrients from its food. They also provide a small amount of energy, but koi do not use them very efficiently. Carbohydrates should make up about 30 percent of a koi’s diet, Neaves said.
Vitamins and minerals help a koi regulate its metabolism, Neaves said. The nutrients work as a team to aid koi in maintaining good health. Koi obtain vitamins from their food and minerals from their food and the pond water.
Ideally, koi receive most of their nutrition from formulated diets supplemented by fresh foods (see sidebar). Manufacturers specially develop formulated diets to provide complete and balanced nutrition for fish in easy-to-feed forms. Common shapes include sticks or pellets that float on the pond’s surface or slowly sink to the bottom of the pond.
FEED IN MODERATION
When feeding koi, remember this adage: “Moderation in all things.” Plan to feed your koi three or four times a day. Koi do not have stomachs in which to store food, Neaves said. They digest their food in four to five hours, so feed them frequently throughout the day.
If given the opportunity, koi will overeat, which can cause illness. Feed them only as much food as they will eat in five minutes. Remove uneaten food with a net.
Even if your koi do not become ill from overeating, the water quality in your pond can suffer from uneaten food left in your pond, Neaves said. More waste means more work for you to maintain a healthy water quality for your fish.
A current trend among koi owners is maintaining good water quality, said Curt Nuenighoff, TetraPond brand manager in Blacksburg, Va. “The trend in koi nutrition is that owners of premium koi are looking for a food that will result in maximum nutrition and minimal waste production, making it easier to maintain good water quality for their pond fish.”
Planting a Koi Salad Bar
Pond plants can provide vital nutrients for your koi, and many fish seem to enjoy nibbling on the plants in their ponds. Several plants can do double duty as decorative elements and koi snacks.
Duckweed is a floating pond plant that can overtake a pond quickly. It requires little care from a pond keeper except regular removal with a net to prevent it from completely covering the pond and blocking out sunlight. Duckweed provides a food source as well as a hiding place for smaller koi. It prefers medium sun.
Fairy moss is another floating pond plant. This aquatic fern can grow rapidly and overtake a pond unless it is controlled. It prefers shade.
Parrot’s feather is an easy-to-care-for floating plant. Its feathery leaves provide hiding places for smaller koi. It also provides shade for the pond. Parrot’s feather is versatile — it can grow in wet soil above water level as well as on the pond surface — so it can be used along the edge of your pond or in rocky crevices. It prefers full sun.
Sweet flag is a background potted plant available in variegated or all-green varieties. Sweet flag requires annual repotting to grow successfully, and it can send out offshoots that can develop into additional plants. It likes sun to partial shade.
Umbrella palm is suited for edge-of-the-pond placement as an accent element. This unusual plant needs to be planted in a 2- to 5-gallon container of nutrient-rich soil. It prefers sun to partial shade.
Water celery can be used as either a potted plant alongside the pond or as a floating plant on the pond. This plant is available in several spotted varieties or all green. It prefers full sun to partial shade.
Water hyacinth can be a prolific pond dweller. This floating flowering plant can be invasive, quickly taking over a pond. It stays afloat thanks to a small rosette of leaves that acts as an air pocket to keep the plant on the pond’s surface. The water hyacinth helps clean the water by absorbing extra nutrients and reducing algae, and it provides hiding places for smaller koi and shade for the pond. It prefers full sun. Because this plant is an invasive species, check with local experts to find out if it can be included in your area. – J.M.
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Koi are natural bottom feeders, but many pond keepers feed them floating pellets, Neaves said. These allow owners to see their fish on the pond surface, which adds to the enjoyment of keeping koi and provides a regular opportunity to check fish for signs of illness or injury.
Weather dictates koi feeding requirements, said Kevin Drees, director of animal care and conservation at Blank Park Zoo in Des Moines, Iowa. The 1,000 koi kept in a ¾-acre pond on zoo grounds are fed according to the weather, he said.
“Here in Iowa (where the ponds get ice), we discontinue feeding altogether during the winter,” Drees said. “It’s a sort of gradual tapering-off as the water temperature drops and the cold-bloodied fish get less active.”
Nuenighoff recommends using the seasonal feeding cycle. “In water temperatures between 39 and 50 degrees Fahrenheit, we recommend a wheat germ-based diet that promotes high digestibility even in low temperatures when fishes’ metabolisms are greatly diminished.
“In the summer, we recommend a complete premium diet,” he said. “In the winter, stop feeding when the fish begin spending most of their time on the bottom of the pond, where the water is slightly warmer than at the surface, or when the water temperature is less than 39 degrees.”
The age of your koi also affects diet choices. Young koi require diets containing 35 to 38 percent protein for growth, Neaves said, while mature koi require diets containing about 32 percent protein.
FRESHNESS IS KEY
When choosing koi food, remember that freshness is required to ensure good fish health, Neaves said. Check packaging for freshness dates, because food loses its nutritional value over time.
If you store the food in clear plastic bags, Neaves recommended keeping it away from light. The food can sweat if exposed to light.
For best results, Neaves suggested storing koi food in plastic containers with tight-fitting lids, and keeping it in a cool, dry place away from sunlight to prolong freshness. If you buy the food in bulk, you might need to refrigerate it to maintain freshness, he added. Bring the food up to room temperature before feeding it to your fish. Do not freeze the food, because this can damage the lipids and the fat-soluble vitamins in the food.
Neaves recommended discarding any food that becomes wet, looks fuzzy or mildewed, or develops an odor that smells like paint thinner. Dispose of any food that shows signs of insect infestation as well, he said.
By taking the time to carefully select and store a suitable koi food, you can enjoy many hours of relaxation and tranquility feeding your fish. You might soon develop your own weakness for feeding koi.
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