A quick and easy way to build an outdoor garden pond is to use a preformed unit that is sunk completely (or partially) into the ground. Preformed units come in many different shapes and sizes in plastic, fiberglass or rubber. After you've chosen the one you want, all you need to do is set it up. Here's how.
Position the preformed unit on the designated location. Prop it up with bricks as necessary to keep it level. Using the preformed unit as a guide, drive sticks or long stakes into the ground to mark the area that needs to be dug up.
Dig the ground to conform to the shape of the underside of the preformed unit. The preformed unit will retain its integrity if the hole is an exact fit.
Clean the hole. Remove rocks, debris and other items that could puncture or compromise the shape of the preformed unit.
Pour the underlay of sand into the hole. The underlay will help keep the preformed unit level, stable and secure.
Slip the preformed unit into the hole and double-check to ensure that the pond is level. Adjust the thickness of the underlay as needed.
Slowly add water to the pond. The weight of the water will help push the preformed unit into the ground. Make sure the pond remains level.
Secure the preformed unit by pouring sand into any gaps along the sides of the pond (between the preformed unit and the ground).
Add decorative edging like stepping stones, slabs, pavers or planters to hide the borders of the preformed unit.
Add plants and decorations. Condition and cycle the water if adding fishes.
Get the most durable preformed unit you can afford. You can clean it without fear of rupturing it, and the water garden will last a long time.