Every time Jena Questen steps into her backyard, she’s greeted by 400 colorful koi that rush to the edge of the pond and flip over each other to get her attention.
“I wasn’t that intrigued with them in the beginning,” she says. “But now I understand why people become attached to them. They’re very interactive and there are some we can feed by hand.”
Questen is an veterinarian with a dual personality. As a mobile vet, she spends the year making house calls and treating conventional pets like dogs, cats and horses.
But during the summer she becomes Dr. Koi.
Questen became interested in treating fish when she learned from her husband, Scott Eddy, how many koi were dying needlessly because they weren’t receiving good veterinary care.
Eddy designs, builds and maintains fish ponds, so he could see the need from both the fishes’ perspective and the pond owners’, too.
Healthy pond, healthy fish
Fish are a product of their environment, so having a healthy pond will increase the likelihood of healthy fish.
Dr. Koi says the four keys to creating a healthy pond are proper depth, adequate aeration and filtration, and good water quality.
The pond needs to be at least 2 1/2 to 5 feet deep, she says. The depth allows koi to exercise by swimming up and down and helps them escape from predators. A deep pond also means the water won’t freeze to the bottom in winter.
Pond aeration is also a factor in creating a healthy environment to sustain fish. Aeration variables include the shape and size of the pond, the number of fish, and how the water is pumped and filtered through the pond. Waterfalls and fountains need to be especially active to generate enough oxygen for the fish.
Because a pond for plants is built differently than a pond for fish, Dr. Koi says it’s important to discuss the requirements with the designer before installing a new pond.
“Even if you think you never want fish, build the pond to sustain them,” she recommends. “It’s more expensive to rebuild the pond if you change your mind in the future or if you sell your house to someone who wants to add fish to the pond.”
Birds, like the Great Blue heron, are also hazardous to a fish’s health. To keep birds away from the pond, Dr. Koi recommends building the pond with steep sides so birds and other predators can’t stand on the edge to go fishing.
She’s also found a physical barrier over the pond, like netting or crisscrossed fishing line, is more effective than using fake alligators or scarecrows to keep predators away.
Just like in nature, a backyard pond needs circulating water, rocks, plants and natural bacteria to keep its ecosystem in perfect balance.
However, if the pond is also home to koi, plants need a little extra care, says Dee Beckman, tropical horticulturist at Tagawa Gardens in Aurora.
“Koi are aggressive fish and they’ll dig up or tear up the plants in the pond,” she says.
To prevent this, Beckman recommends placing plants around the edges or margins of the pond, where they can do their work as nature’s pond cleaners, but where the koi can’t get to them.
Build a dam for planting
She says to create a dam with rocks in the shallows of the pond for a separate planting area. Then either place potted plants in the dam or plant them directly in the dam using weed barrier or burlap and an aquatic plant soil that won’t cloud the water.
Plants that live around the edge of the pond are called marginals, and there are hundreds to choose from, Beckman says. Her favorites are water celery (Oenanthe japonica) and water clover (Marsilea). Others include cattails (Typha), taro elephant ear (Colocasia esculenta), and umbrella palm (Cyperus alternifolius).
Beckman warns these plants can be invasive, so they need to be cut back on a regular basis or they’ll outgrow the pond.
Jodi Torpey’s book, “The Colorado Gardener’s Companion: An Insider’s Guide to Gardening in the Centennial State,” is available on her website, .
