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Koi Pond: Home Projects

Koi Pond: Home Projects
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Project: Indoor-outdoor koi pond

When John and Charlotte Pratt relocated to Bethlehem, Connecticut, they transported the koi from their outdoor pond in a horse trough. Charlotte dreamed of having a place in their new house where she could enjoy the fish year-round.

She now has a pond in the breakfast nook where she and her husband commune with their koi every morning. (Afterward, she tends her horses, chickens, cats, dogs, turtles, and parrots.)


John designed a 4×8-foot pond that is 4 feet deep, and the couple built it over two years. The genius of this 800-gallon pond is that the fish can swim outside, slipping under a granite sill that serves as an air lock. John describes it as “an aboveground pool in the middle of the house foundation.” Radiant heat in the tile floor keeps the water temperate inside, and sunlight does the job outside. John figured the water could present 1,000 pounds of force, so they used rebar and 70 bags of mortar mix for reinforcement. “Working on it was so much fun,” recalls Charlotte. “We bought one pallet of flat stones, and for the rest we went ‘rock shopping’ in our yard.” Using masonry screws, they attached rocks to the curved cement walls for a natural-looking exterior. The Pratts installed a heavy-duty liner, which they ordered from a specialty catalog for fish hobbyists. There is an intake hose with filter and fan in the pond, a little waterfall for aeration, and an additional filtration system hidden in the pantry, where Charlotte and John have access to the pipes for back flushing.

Cost: Just under $2,000

This includes the $700 filtration system and $300 for the granite sill.

What do you like the most?

“The fish have grown very friendly because they have so much human contact,” says Charlotte. She wiggles her fingers in the water and the fish come immediately, looking for food.

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Updated Tuesday, April 10th, 2007

One Response to Koi Pond: Home Projects

  1. anita boyd September 11, 2011 at 3:26 pm #

    Is there more detailed info. specs etc

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