Liners are necessary for any permanent body of water, and are especially useful to maintain water levels and quality within nursery ponds. The ideal liner for a nursery pond is able to prevent the leaching or absorbtion of dangerous toxins, and is resistant to frequent drainings or maintenance. Some materials may be damaged by the sun-baking or freezing and breaking associated with the refreshing period in seasonal nursery ponds, like clay or concrete. Porous materials like clay and concrete are also more likely to absorb and eventually leach chemicals or toxins back into the water it's in contact with. This can be assisted or even prevented by the use of an impermeable, durable liner.
