A Koi Pond

The back yard of David and Judy Blake's San Francisco home features a beautiful expanse of lawn but doesn't offer much in the way of visual interest. To add color and aesthetic appeal to the site, the couple has decided to add a koi pond in the area near the back patio.

To implement the project, the Blakes enlist the help of contractor Jim Wilder, who says water gardens offer a number of benefits, chief among them soothing sound and tranquil beauty. Wilder estimates that a professional installation would cost around $7,000 (using a sophisticated pump and filter system such as the one used here), whereas the average do-it-yourselfer can expect to spend about $2,000 for the required materials. Wilder also explains that the project requires a great deal of physically challenging labor and the average homeowner would need about four weekends to complete the work. On a difficulty scale of 1 to 5, with 5 being the hardest, Wilder rates the project a 5.

To get started, the crew first clears the area where the water feature will be located. Once the workers remove the turf, they use landscaper's marking paint to outline the shape of the pond and the cascade that will provide the structure for the waterfall . (A gently rounded shape gives the pond a natural look; Wilder recommends avoiding straight edges.)

Next, the crew digs the hole for the pond to a depth of 2 1/2 feet, carefully following the outline. All ponds with fish must be dug at least 2 1/2 feet deep: predators pose a threat in more shallow water. The dimensions of the pond measure about 10 feet by 12 feet.

Crew members build up one side of the pond--topped with a few stones--to compensate for an existing slope. This will create a level bed for the water once the pond is filled. Then they dig out a ledge along the perimeter of the pond, about two inches below where the surface of the water will reach. This will serve as a starting point for building up the stones.

Finally, the crew digs a trench from the pond to the top of the cascade. Inside the trench workers lay a 1 1/2-inch length of PVC pipe (sold in home centers) that reaches from one end of the trench to the other. This will allow the water from the pond to be recirculated to the top of the cascade. Wilder notes that this is a good time to lay any low-voltage power lines that will be used for lighting as well as the electrical line to power the pump.

Step Two: Lining the Pond and Adding Plants

For this project the crew uses a professional-grade external pump (and filter), which is stronger and easier to maintain than other types of pumps. Homeowners who want to keep costs down and keep the installation relatively simple may prefer a submersible pump. Wilder notes that submersible pumps have a relatively low usage cost--about $5 a month when running full time.

After installing the pump and filter, the crew begins lining the pond . The first step is to remove any rocks or sharp objects that could puncture the liner. Next, the crew lays landscaper's cloth (available in home-supply stores) and cuts a hole to accommodate the end of the return pipe.

Crew members then attach a bulk head fitting (available in pond-supply stores) to the end of the pipe where it emerges from the fabric: this permits the liner to be sandwiched next to the landscaper's fabric to prevent leaks.

With the landscaper's cloth in place, the crew lays a layer of sand over its surface to hold it in place. Then workers begin laying the liner, made from a heavy PVC material that costs about $1 per square foot and can be found in home-supply stores. The crew lays the liner so it covers the entire pond, with enough excess hanging over the sides so it won't be pulled too small when the rocks are put in place. Now the workers add water to the pond to fill the liner and weigh it down.

Finally, they cut a hole in the liner to allow the return pipe to emerge and finish attaching the bulk head fitting, making sure it's secured tightly.

While the crew finishes adjusting the liner, garden designer Dorothy Nickolai sets to work on the planting plan. Nickolai says her goal is to add color and interest without overwhelming the area. She explains that the plants will create a setting for the pond that helps integrate it with the surrounding garden.

Inside the pond Nickolai adds several water-loving plants for strong visual impact, then plants a variety of colorful, low-growing shrubs and grasses around the pond's perimeter (all the chosen plants are suited to a pond setting). Featured plants include the following:

• Hibiscus moscheutos, Zones 5-10
• Cardinal flower (Lobelia cardinalis), Zones 4-8
• Waterlily (Nymphaea 'Hermine'), Zones 4-11
• Dwarf red canna, Zones 8-11
• Zephyr lily (Zephyranthes candida), Zones 9-10

Note: In colder climates, the dwarf red canna and zephyr lily should be brought indoors during winter.

Step Three: Setting the Stones

Wilder has chosen Sonoma fieldstone from which to construct the pond. He explains that it is local to the area, is inexpensive and has a great texture, covered with mosses and lichens that will enhance the pond's natural look. The stone's appearance is similar to that of stone used in other areas of the property, which will help unify the pond with the landscape.

Wilder explains that it's important to select stone that will hold up well underwater. He recommends checking with local building-supply stores to find a suitable type.

The crew begins building up the stones from the ledge inside the pond, working upward. Wilder explains that it's a good idea to work in small sections to avoid getting too far ahead without evaluating the pond's appearance. He also recommends avoiding straight lines when laying rocks in place to maintain the natural look.

Next, the crew moves on to the mortar, mixing it with dye so that its color blends better with the rocks. (Mortar dye is available in most hardware and home-supply stores.) Wilder says the consistency of the mortar should be just thick enough to adhere to the rocks. Wilder suggests using small pieces of rock or cinderblock as supports to prop up larger stones and help wedge them into place.

Once the ledge is in place, the workers move on to the cascade--first building up the walls, creating a curving path to give the water a natural flow. They integrate several flat stones into the cascade to serve as "spill stones": these will create mini-waterfalls along the cascade and into the pond. The spill stones must be level to ensure that the water flows properly.

To fill in between the rocks and hide any areas of exposed liner, the crew uses 1/8- to 1/4-inch Mexican gravel mix, available in rock and sand specialty stores. To hold the gravel in place, they first add additional mortar around the stones that are already laid, then sprinkle gravel over those areas and pat it down.

After allowing the mortar to set for about two days, the crew fills the pond with water to check for leaks. Once the pond has been deemed leak-free, workers treat the water with dechlorinating chemicals to remove chlorine and chloramine, both of which are poisonous to fish. Now they're ready to add koi.

Step Four: Adding Koi

Koi expert Bob Gordon says koi are ideal for a backyard pond because they're beautiful and playful and can be hand-fed. When selecting koi, Gordon advises looking for active, fast-swimming fish that are integrated with the others; avoid fish that are isolated as well as any with signs of injury such as split fins.

Koi, which generally range from four to five inches in length, cost about $20 apiece and can live to be more than 100 years old. He also notes that the fish will eat floating koi food but are easily overfed because they like to nibble all day. As a precaution against overfeeding, give the fish just enough to eat for a four- or five-minute period. Koi generally eat more in warmer temperatures, less in cooler temperatures. Finally, Gordon explains that koi should be brought indoors and kept in an aquarium during winter in climates where temperatures drop particularly low.