Backyard Koi Pond

Japanese koi each need at least 2 square feet of pond surface by the time they are fully grown.

The focus of this garden is a 1,400-gallon Japanese koi pond and waterfall surrounded by a footbridge, paths, boulders, statues, and lush plantings. These homeowners did their own design and construction; follow their ideas to create your own water garden.

continue reading below

What You Need:

  • Sand
  • Polyvinyl chloride liner
  • Aquarium sealant
  • Spray-foam insulation
  • Koi, snails, frogs, toads
  • Water pump
  • Pond heater (depending on climate)


Koi fish

1. Plan for a surface area of 50 or more square feet (such as an 8-foot-diameter circle or a 5 x 10-foot rectangle), and a depth of 1 1/2 to 2 feet.

2. Line the sides and the bottom of the pond hole with 2 inches of wet sand. Top this with a polyvinyl chloride liner, extending the edges above ground. We used extra pond liner material, plus aquarium sealant and spray-foam insulation, to ensure a water-tight foundation.

3. Build the pond in partial shade; full sun makes the water too hot and allows algae to flourish.

Note: If you live in an area with severe weather, take the fish inside in winter. In milder climates, fish can live under a foot of ice with an air hole created by a pond heater, which is often called a “floating deicer.”

4. Add snails, frogs, toads, and turtles to help control insects and algae.

5. For a waterfall, install a pump that circulates half the pond capacity per hour.