I'd be more concerned with prep and construction vs poly.
Pond bottom must be built on solid ground below frost line no backfill unless compacted gravel. Outside must be well drained at depth of pond. This helps to prevent outside freeze thaw and hydrostatic pressures on pond walls. Put 1.5 to 2 inch high density foam on the outside of the pond starting at soil level down. This allows a cushion from ground side seasonal forces and helps to stabilize pond temperatures. Use crystalline waterproofing in concrete.
Last edited by batman; 06-21-2020 at 10:03 AM.
The real Batman wears polyester! Don't be fooled by the plastic imposter.