How thick should a fish pond liner be?

-For the fish ponds, 0.5mm 0.75mm 1mm thickness is popular, because the pond liner should have a tensile strength, and puncture resistance, the sharp rock and  tree branches cannot damage the pond liner easily. And these thickness is flexible, not heavy, easy to install.

How long will a pond liner last?
-The pond liner can last 6-60years based on different pond conditions. The pond line life is normally affected by the sunshine, temperature and For fish pond liner, 0.75/1mm thickness hdpe pond liner can last 10-20years exposed to the sunshine, and 20-60years buried without sunshine. If the pond liner is used for the landfill,oil gas,mining projects, the hdpe liner should be buried, and the liner life should be >60years even 100years.
Do the fish pond need pond underlay?
-The pond underlay is used to protect the pond liner, for example, the geotextile fabric.  Normally the fish pond chooses a thick pond liner, which is puncture-resistant, and not easy to be damaged. If the budget is enough, the underlay can be used.