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.
A durable liner is ideally resistant to the UV radiation that exposure to sunlight will involve. It'll also be able to handle the frequent maintenance and movement that's involved with ensuring ideal conditions for sensitive fry. It'll also need to be fish and plant safe, especially if the fry are intended for direct human consumption. This means that the material can't leak plasticizers or other chemicals into the water that can kill fish and poison humans. BTL's AquaArmor (https://www.btlliners.com/aquaarmor) is rated by the international NSF as the highest quality material available for transporting or storing water meant for human consumption. Additionally, BTL's products are food and plant safe, ensuring the health of your growing fish.
