How to Create a Backyard Pond

Step 1: Know the anatomy

A free-form pond can be customized for any landscape, with different rocks, plants, shapes, and waterfalls. But we’ll give you some helpful points on placement, size, and materials.

Before you start, call 811 or your local one-call center to have electric and gas lines marked so you know where to dig to steer clear of them. Then, when you map out the location of your pond, put it where it will be noticed—visible from a window, off a patio, or along a walkway—but away from the play areas of small children or pets. Keep clear of major root systems or mature trees, which can block too much of the sunlight plants and fish need. You’ll also need to be within reach of a grounded exterior outlet so you can plug in a pump, an essential tool for keeping the water aerated; most pumps come with a maximum cord length of 25 feet, and extension cords are not recommended. You may need to bury the power cord a few inches down in PVC pipe to hide it.

Space permitting, you need at least 40 cubic feet for your pond—about 7 feet by 4 feet—to keep the water clean. An initial shallow terrace just inside the perimeter of the pond holds rocks that conceal the liner edge and keep it in place. A second, deeper terrace supports plants that live in the water and help balance the pond’s ecosystem. As you dig, you must slope the sides of the pond so that if the water freezes, the ice will push up instead of against the liner. Even in warmer climates, small ponds can change temperature rapidly, so if you’re adding fish you’ll want a deeper pond that will maintain a more consistent temperature and accommodate the fish—18 to 24 inches for goldfish and at least 3 feet for koi.

To maintain the consistent depth of the water, you need to line the pond. A thin layer of sand and old newspapers or burlap bags softens the jagged edges of rocks and roots. But over that you will need to put a waterproof skin. There are several types of flexible liners meant for small ponds—made from polypropylene and EPDM, among other materials. Look for one that’s weather-resistant, so it will stand up to UV rays and freezing temperatures. It should also be rated “fish-safe” if you plan to stock your pond and come with a warranty of 10 to 20 years so your pond will be watertight for many years to come.