What is the best pond liner for a Koi pond?

There are different options for lining a koi pond, depending on the size, shape, and budget of your project. Some of the most common choices are:

• EPDM rubber liner: This is a flexible and durable material that can conform to any pond design. It comes in thicknesses of 45mil and 60mil, and is resistant to UV rays and weathering. Most pond builders use 75mil EPDM pond liner.
• Underlayment and plastic liner: This is a cheaper and easier option that involves laying a layer of underlayment, which lets gas escape between the ground and the liner, and then covering it with a heavy-gauge polythene sheet. This method works well for small and simple ponds.
• Concrete: This is a more permanent and expensive option that requires more skill and labour. Concrete ponds need to be reinforced with steel bars and mesh, and then coated with a waterproof sealant. Concrete ponds can last for decades, but they also need more maintenance and cleaning.

The best way to line a koi pond depends on your personal preference and the characteristics of your pond. You should consider the size, depth, shape, location, and budget of your pond before choosing a liner. You should also research the pros and cons of each option and consult a professional pond builder if you need advice.