Size

• Concrete can be poured to create a koi pond of any size or shape. Liners also are available in a variety of sizes and shapes. Concrete and liners are both viable options, no matter what size pond the owner is looking to create. Ideally, the pond should have shelves, with the shallowest shelf being around 12 to 18 inches deep and the deepest shelf being at least 24 inches deep. To keep koi, a pond with a minimum of 1,000 gallons is recommended.
  
  

Cost

• The cost of concrete for a koi pond can vary based on the individual brands of concrete available. Bags of concrete are readily available at major and local home improvement retailers, with the price per bag ranging from $2 to $15. Meanwhile, a liner can cost significantly more. At the low end, pond liners for koi ponds start around $45 and can go up into the low $2,000 range.
  
  

Durability

• In terms of durability, both concrete and liners have their pros and cons. For example, concrete is more durable against issues like children throwing toys around, such as lawn darts. Toys could easy scratch, rip or poke through a koi pond liner, draining the water and requiring replacement of the liner. However, a liner will better contract with the changes in season, whereas concrete may crack in the cold weather with expanding ice in the pond or the expanding soil around the pond.
  
  

Lifespan

• The lifespan of a pond liner can vary based on the product, the manufacturer and the location in which the pond is placed. For example, the lifespan of a vinyl PVC pond liner is around 10 years, wheres an ethylene-propylene rubber (EPDM) pond liner can last 20 years. However, this does not take into account the potential for damage from tree roots or underground pests. Concrete, on the other hand, can last for several decades when properly installed and maintained, according to Aquamedia Corp. CEO, Douglas C. Hoover. Though concrete cannot be affected by underground pests, roots can still cause damage, such as cracks.