Dig A Hole
Digging a shallow pit and filling it with a layer of concrete is the simplest way to build a concrete pond. Only shallow depth is possible with this method, and the concrete will not be as strong as the walls produced by other methods.
Using simple wood forms helps you build stable vertical walls, adding depth to the pond, according to the Agricultural Extension Service of Texas A&M University. The forms keep the wet concrete in place until it is strong enough to stay in shape on its own.
Adding reinforcement bars made from steel, such as rebar, makes the concrete even stronger. This allows for taller and straighter walls than the use of concrete forms alone. These reinforcements are added when pouring the concrete and must be completely enclosed to prevent rusting.
When concrete is applied with a high-pressure sprayer it is known as gunite. This application works well for concrete ponds, states the Langston University Extension Office. Spraying the material on allows it to stick to the walls of the pit you dig without requiring as much work as spreading it by hand.
While it is possible to use a mechanical pond filter with a concrete pond, a natural filtration system also works. This is accomplished by installing drainage pipes in the concrete that send water through a gravel bed below the concrete of the pond, according to Bradshaws Direct.
For a deep and rectangular or square concrete pond, use preformed blocks. Lay a foundation of smooth concrete, recommends Koi Water Garden Ltd. and then stack the blocks and fill them with concrete.
Concrete contains high concentrations of lime that leak into the pond's water over time. Installing a flexible plastic or vinyl liner prevents this leeching effect, according to Bradshaws Direct. These liners come in a variety of colors and are easy to install.
If you don't want to add a liner, use a concrete sealant to keep the water quality level. Sealants require reapplication every two to three years, per Clearpool, which requires draining and cleaning the pond. This may be impractical for a very large concrete pond.
Digging out extra space around the edge of the pond allows you to pour concrete footings. These supports are known as footings and help prevent the weight of the concrete and water from causing the pond to sink deeper into the ground, according to Wet Web Media.
Laying a layer of wire fencing between the soil and the concrete pond wall helps the concrete stick to the walls of the pit you dig, according to "Mother Earth News." If you don't plan to add rebar or use forms, this may be the only way to keep the concrete from slumping into the center of the pit.