To build a fish pond, first select a location for the pond. Site the fish pond in a flat, open area that receives maximum sunlight. Test the soil by digging a 3-by-5 foot hole about 4 feet deep in the center of the pond. Fill the pond with water and see if the water remains in the hole before seeping into the ground.
Start digging the pond from the center, working towards the shores while creating a slope around the perimeter. About 15 percent of the pond should be 10 to 15 feet deep, dropping gradually from the shore or underwater ledges. Dig the sides straight down. Align the sides of the pond using a straight plank of wood and a spirit level. Use a hand trowel to level out all the areas in the pond.
Create the shallow part and the deep end of the pond. The center of the pond should be approximately 15 feet deeper than the top. Allow space for the plants desired. Eliminate the roots and rocks that might affect the lining of the pond. Use your hands to examine areas of the pond for such obstructions; use the trowel to dig them out.
Fence the perimeter and add aquatic plants to keep water and soil fresh. Fill the pond with water and allow it to sit for a day or two. Test the water and then stock the pond with fish from a licensed hatchery.