Firestone 10 x 30 PondGard 45 Mil EPDM Pond Liner Fish Safe 45 Mil EPDM Fish Safe Liner with a 20 Year Limited Manufacturers Warranty. This Top Grade Tear and Puncture Resistant 45 mil EPDM liner is perfect for adding a stream or for lining your waterfall. Never settle for PVC or anything less than 45 mil EPDM PondGard Liner. PondGard remains flexible in a variety of temperatures, from -45 F (-43C) to 180F (82C), enabling it to be installed year round in a variety of climates and terrain. PondGard is a specially formulated EPDM membrane designed to be used safely in the presence of fish and plant life.