average cost to install interior koi pond
Typical costs: 1  There are many kits available online, with prices ranging from $450 for a 6-foot-long, 6-foot-wide pond to $5,500 for a 34-foot-long by 34-foot-wide pond.  Professionally installed koi ponds cost up to $50,000, depending on the pond's size, the experience of the contractor and the materials used.