Koi consider waterlilies a delicacy, so if you want a pond with fish and flowers, give your koi regular feedings so they won’t munch the blossoms. Koi also like treats like watermelon, peas, rice and cereals.

Japanese koi like these are prized for their exquisite jewel-like colors. A young Japanese koi costs about $75, but will grow into a $6,000 fish that may outlive you, since a koi’s average life span ranges from 20 to 90 years or more. The oldest koi on record recently died in Japan at age 225.

Debbie Weingardt, of Bestway Imported Koi, raises Japanese-imported koi at her pond in Broomfield.

Koi Craze

More and more homeowners are “playing koi” and discovering the serene beauty of raising these colorful fish in ornamental ponds.

by Debra Melani
photos by Erik Paulsrud Photography

Don Coen skirts the edge of his pond, tossing handfuls of pea-sized pellets into the slowly rippling water. The soft bubbling sounds quickly give way to loud sucking noises, as a large, round koi mouth breaks the surface to snatch the pellets. In a flash, streaks of orange, red and black glide below the glassy water, and a tail fin flips a goodbye-like wave.

“They’re extremely therapeutic to watch,” Coen says of his dozen dappled koi. “They’re beautiful. My dad used to come over and just sit here for hours.”

Coen is one of an increasing number of locals getting hooked on koi, a Japanese fish related to the carp, but often referred to as “pond jewels” because of their exquisite colors. The Boulder artist built a koi pond inside his foyer 10 years ago.

But the majority of koi enthusiasts have outdoor ponds, which means their fish lie dormant at the pond’s bottom in winter, where they’ll doze until the first signs of spring. It isn’t too early for wannabe koi owners to start planning a pond, though, and preparing it for fish introduction when the tulips and daffodils bloom. Ask Steve Johnson, and he’ll tell you: Forethought is worth its price in koi.

“I just dug a hole and threw in a liner,” Johnson says, referring to his first attempt at raising koi a decade ago. “I made a bunch of mistakes. It’s better to find somebody who has done it and learn from them.”

Johnson, now president of the 150-member Rocky Mountain Koi Club, says everything from choosing the site to equipping the pond to buying the fish can make or break the koi experience.

Site to Be Seen
Coen’s 3,000-gallon pond appears at home in his grand foyer, which boasts a 26-foot-high ceiling, massive entryways and an open staircase. His indoor site has some advantages: “I don’t have to worry about herons or raccoons eating my fish, and I don’t have to worry about debris falling in the water,” he says.

For those who prefer a natural outdoor setting, Debbie Weingardt suggests picking a site close to your home that’s on a high spot, so pesticides and fertilizers don’t wash down into the pond and kill plants and fish.

“It’s just a lot more fun to look at [the pond] over the deck or off of the back porch than it is to walk across an acre to see it,” says Weingardt, who has been raising koi for 32 years and owns Bestway Imported Koi in Broomfield.

For Charlotte Knudson, having her pond next to the patio of her Wonderland Hill house keeps her “pets” closer to home. An eight-tiered waterfall slowly spills into Knudson’s pool of koi, offering a tranquil setting for her and her husband. “They’re very friendly,” Knudson says of her fish, while leaning down to swirl a stick in the pond. “They come to movement.” Sure enough, the swishing quickly attracts some of her 30-plus fish.

That attraction to movement can be a death knell, however; something Knudson learned the hard way. Because her yard backs to open space, she’s lost some koi to predators. Now two crane statues guard each end of her pond, scaring off the herons, as long as she routinely rotates the fake birds. And any critter that steps too close to her pond’s edge gets a blast of blaring noise from a motion-sensing alarm. Both tactics have worked well, she says.

A pond’s size and design can also protect koi from predators, says Weingardt, whose longest-lived koi is 48 years old. She recommends a 3- to 5-foot depth with steep sides; a shallow pond with sloping sides offers critters a dinner invitation. Deeper ponds also provide more hiding places and warmer pockets beneath winter ice, and they help prevent sunburn (koi can suffer from skin cancer).

One of the most common mistakes Weingardt sees is people digging too small of a pond for the number of fish they end up wanting. “I tell people to build it twice as big as they thought they were going to build it.” The belief that koi will grow according to the size of the pond is a fallacy, she says. “It depends on the ­breeding.” Some koi grow to 8 inches in length; some grow to 5 feet.

Winter pond digging might require machinery, if the ground has frozen. Always check with the Utility Notification Center of Colorado (1-800-922-1987; uncc.org) before sinking the first spade; the organization can help you avoid issues with cables, pipes and gas lines.

Once your site is prepared, you’ll need to line it. Weingardt uses 60-65 mil EPDM rubber roofing for her liners because of its 50-year life span. “We had an 8-ton rock fall on it, and it didn’t puncture. A lot of people used to use a vinyl liner, and those things will crack with the first hailstorm.”

Concrete ponds are also a poor choice, because of the potential for freezing and cracking. In addition, they pose an injury risk for koi. “During spawning, the males body-slam the females into the sides to push out the eggs,” explains Weingardt, who strongly advises against using decorative rocks in ponds for that same reason. Rocks also allow a breeding place for bacteria that can infect koi.

A properly built pond can be nearly maintenance-free, says Weingardt, who also suggests installing a bottom drain through the liner to self-clean, a skimmer box, and and an out-of-pond pump and filter. Choices vary, and Weingardt invites anyone to contact her for free advice (see “Koi Resources” on this page). She also notes that excess chlorine can kill koi, so when filling ponds with city water, add a de-chlorinator before setting fish free in their new home.

Fishy Business
Serious koi hobbyists often choose fish imported from Japan, where the focus is on breeding the most colorful fish and less on mass production. A good, young koi will cost about $75, but will grow into a $6,000 fish, says Weingardt, who has fish worth $20,000 among her 1,000-plus collection. Some U.S. breeders offer much less-expensive koi. Koi may also outlive you. Their life span ranges from 20-90 years or more. The oldest koi on record recently died in Japan at the ripe old age of 225!
No matter where you buy your koi, make sure they were quarantined and treated for bacteria and parasites. “Otherwise, you could buy a really sick fish and contaminate your pond,” Weingardt says.

Many koi owners also advise against introducing goldfish into a koi pond. “I decided to put in a couple of goldfish,” Johnson says, “and not long afterward, I pulled 160 goldfish out.” Rapidly reproducing goldfish not only overwhelm a pond, they also carry parasites and bacteria that don’t affect them, but do kill koi.

Once you’ve bought your fish, routine feedings are crucial, especially for ponds that mix koi and prized lilies. “Those [plants] are like a delicacy for them,” Johnson explains. “But if you feed your fish regularly, they don’t usually bother the plants.” He recommends koi pellets, but says koi also enjoy treats like watermelon, peas, rice and cereals.

Feedings should end after outdoor temperatures fall below 50 degrees. Digestion stops during a koi’s winter dormancy, and continued feedings can kill the fish. During cold months, koi owners must also maintain a hole in the ice for aeration. Then, be prepared to miss your wet pets for a while.

“Last year, there were about two and a half months where I didn’t see my fish at all,” Johnson wistfully says.

But come spring, come koi—and joy. “It’s an absolutely gorgeous pastime,” Knudson says. “So quiet and serene.”

Debra Melani is a freelance writer who lives near Lyons, where she fears a koi pond might attract bigger critters than raccoons. For now, she’ll stick with watching trout in nearby streams.

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