Pond underlayment has only one job and that is to protect your pond liner.
Pond underlayment carpet.
Cattle crossing carpet and gravel or dirt access roads.
Garden and commercial landscape fabric.
A medium weight underlayment for soil separation and stabilization in paving and gravel applications.
Carpet is sometimes suggested as a pond liner underlay and you might get away with this just ensure that the carpet is a man made fibre such as polypropylene as a natural fabric such as wool will rot over time reducing it s effectiveness as a barrier and leaving the pond liner exposed to danger.
Heavy duty weed barrier.
The underlayment is light in weight spreads easily and has a non slippery surface making installation quick and easy.
Liner and underlayment epdm pond liner is extremely flexible and will conform easily to whatever shape pond your desire.
There are many different pond liners to choose from but you should know that 45 mil epdm is the standard for decorative fish ponds here in america.
Pond underlayment provides additional protection for flexible rubber or plastic liners.
Rock and boulder padding.
Aquascape non woven geotextile underlayment is used to protect pond liner from rocks roots and other sharp objects that may damage the liner.
Walkway driveway patio under paver.
Since patching systems require a clean and dry surface on which to bond a puncture to the liner typically means draining the pond for a repair.
A proper underlayment is considered a non woven geotextile that is a fancy term for saying it is a really tough material that is lightweight and easy to work with.