Concrete ponds, if properly constructed, can last a lifetime. In addition, they can be constructed with vertical walls to increase the ratio of gallonage to surface area. However, this material is generally expensive and requires much skill to install. If hiring the work done, ask for references and check them. Hire experience! Whether you or someone else builds a concrete pond, a poorly constructed pond will cost more to maintain, repair or replace than it did to install. This is the main reason for the popularity of the new synthetic construction materials.
The basic construction of a concrete pond follows that of the liner ponds. The concrete should be 4 to 6 inches thick. Once the dimensions are established and an outline laid out, dig out the soil for the entire pond. Forms must be built in place to hold the concrete while it dries and cures. Concrete reinforcing bars must be cut to size and fitted into the construction. The pond must usually be poured all in one day and in one piece, or if large, in sections. Start with the bottom, then the sides, shelves, and, lastly, the top and any coping around the edge. Any junctions of ponds poured in sections are critical as the site of future leaks and weakness to the shifting aspects of the soil. An alternative is to pour the pond without forms and simply slope to the walls and pour the concrete thicker to hold the concrete in place. However, this procedure can produce weakness in the concrete itself due to low density and air pockets as well as being a problem to plant and maintain.
Once the pond is built, it must be treated to correct the basic nature of concrete which would affect the pH of the water. The pH of the water may need periodic adjustments for some time after construction. Lastly, the color of concrete must be changed for the pond to look right. Apply a pool paint or masonry sealant containing a dark pigment. This will conceal the bottom and moderate the pH of the pond.