The doctor reached down to lift her patient, who suddenly jumped free and landed with a thud on the floor.

No harm done, though — and it's her fish. She picks him up and deposits him in a container of water.

The patient is a 2-year-old koi, a species bred in east Asia hundreds of years ago to add flashes of brilliant color and life to ponds and water gardens.

The doctor is Jena Questen — more popularly known by the nickname Dr. Koi. She is a veterinarian (Colorado State University, 2001) who later trained herself to treat ornamental fish because she saw so many of them dying needlessly.

On this day, Questen was demonstrating fish care to visitors at the Denver Holistic Center, a mélange of mainstream and alternative animal care practices in north Denver. She maintains Colorado's first fish hospital there.

And her treatments run the same gamut as those for other species: exams, vaccinations and x-rays, ultrasound and surgery. Like others who've encountered her work, this crowd was curious about the details.

For example: How do you know if a fish is sick?

Answer: There are a variety of clues.

"No. 1, if it's not swimming naturally," Questen said. "Or if it swims apart from other fish. If it's not eating. If there is obvious swelling. If it has growths or injuries."


She plucked a wriggling, silver-white koi, 8 inches long, from a large fish tank to demonstrate. She placed it in a plastic bucket filled with water and picked it up, turning it over to inspect it.

That's when the fish tried to make its desperate escape. The guests gasped. But Questen deftly returned the uninjured koi to the bucket.

"He had reddened fins," Questen said. "That indicates an injury or bacteria."

Questen points out an area on the fin that has turned bright red, which is similar to a human&#8217;s bruise-type injury.
Questen points out an area on the fin that has turned bright red, which is similar to a human's bruise-type injury. (Kathryn Scott Osler, The Denver Post)

She routinely scrapes scales from each fish she examines to check for bacteria. The cure for either malady will be antibiotic injections or baths.

Another common question: How the heck do you operate on a fish?

"Many people are bewildered by the notion," she said. "They ask if I have to go underwater to do it."

The answer is no. You bring the water to the fish.

To show how, Questen set up two plastic containers, each about a foot tall and 14 by 18 inches wide and long. One sits on the exam table, the other on the floor, with both connected by a hose.

To perform fish surgery, Questen adds an anesthetic in the top container's water. Then the lower container gets a lid with a sponge cover, into which a "V" shape is cut. During the procedure, the fish is placed in the "V." Water from the upper container is continually pumped over it to keep the fish oxygenated and medicated.

Questen started treating koi in 2005 when she began working with the Rocky Mountain Koi Club. Her patients include other fish species as well — goldfish, bettas (also known as Siamese fighting fish) and cichlids (the fish family that includes angelfish). She also sees mammals, including dogs, cats and horses, at the clinic and through her mobile practice, East West Vet Service. And she consults, teaches, makes educational videos and does public appearances.

But her main focus on koi, a word that comes from the Japanese word for carp. Her "Dr. Koi" moniker is on a vanity plate that once adorned her car, but now hangs in the clinic.

Owner dedication to this ornamental fish can run to extremes. Koi typically live about 50 years, much longer than a dog or cat. Koi can be an expensive investment, with fanciers booking international plane trips to view and buy them.

"The priciest one I've worked on was worth $26,000," Questen said. Her typical fee to treat a koi runs about $175 to $250.

But a fish's price or rarity is no indicator of its owner's devotion, or willingness to consult a vet.

Jena Questen examines Patch, a 2-year-old male koi.

"The most memorable client I had was a gentleman with a pleco" — also known as a sucker fish, a popular fish in aquariums for their ability to keep tanks clean. "He went to the grocery store every day for 30 years to get the kind of squash the fish ate."

Questen is the only Colorado koi veterinarian listed in the website Nationally, koi specialists are a rare breed themselves, although some general veterinarians treat the species.

That may be changing, according to Steven Smith, a Virginia Tech professor who is president of the American Association of Fish Veterinarians. He says his organization is trying to expand the concept of veterinary medicine.

After all, Smith said. "There are 70 million dogs in America, 75 million cats.

"And 151 million pet fish."

Contact John Davidson at

Know more about koi

Rocky Mountain Koi Club,

Denver Holistic Center: 4640 Pecos St.; 877-585-5444;