Just Liners provides four choices of aquaculture membranes, Firestone PondGard EPDM (Ethylene Propylene Diene Monomer), a type of rubber, PVC (Polyvinyl Chloride), Polyethylene (a thermoplastic) and UltraGuard (a polymeric alloy). Our Geo-Pad Underlay is a polypropylene nonwoven needlepunched fabric. It resists degradation due to ultraviolet exposure. Geo-Pad is non-biodegradable. It is resistant to commonly encountered soil chemicals, mildew, insects and rodents. This fabric will prolong the life of your pond liner by protecting it from rocks and tree roots.