Items you will need
Paint and rollers, stucco or other decorative covering
How to Build an Indoor Koi Pond. Building an indoor koi pond is a great way to bring the outdoors in, and is a beautiful, serene addition to your home. They are also great places to keep koi during harsh winters. Koi ponds take a lot of work, though, and you should invest some time and research into building and maintaining a pond before you decide to go for it.
Choose an area that gets plenty of natural light, or you might find you have less-vibrantly colored koi and struggling plants. Alternatively, halide lights can add artificial light that will help your pond thrive.
Place your pond near a window, door or sink for easier maintenance. You'll likely have to replace some of the water in the pond often, like in an aquarium.
Check your floor for any weak spots before building. Once filled with water, your pond will be very heavy. Many people choose to put their pond next to a study wall.
Build a custom pond using a rubber or PVC liner such as those sold at Tse Koi (see Resources below). Koi do best in ponds that are at least 3 feet deep, and dark-colored liners will make your koi stand out.
Buy a high-quality filtering system for your pond. A filtering system is even more important indoors than outdoors because a poorly filtered pond can leave an unpleasant odor in your home. Keep the size and sound level of the system in mind when shopping. Calculate your water capacity and learn about pond filters at PondLiner.com (see Resources below).
Build a frame for your pond out of 2-by-4-inch or larger boards. Make sure there is enough room in your frame for your pond and a ledge, if you want one to place plants or other decorative items on. Use high-quality brackets to connect your lumber to form a sturdy frame.
Place your pond liner inside your frame.
Cover your frame with plywood. After your pond walls are assembled, you can decorate them by painting them or covering them with some other material to complement your decor.
Indoor ponds are great places to keep your koi during harsh winters.
An indoor koi pond will raise the humidity in your home and could even cause mold. Adding a dehumidifier will protect your home. Koi are best kept in ponds with vertical sides, as koi can jump up and out of a sloped pond. Build your pond tall enough to keep your water level about 6 inches below the top of your pond. This will keep koi from jumping out.