PVC pond liners are NOT generally considered the safest option for fish ponds or food-related aquatic environments. While some PVC liners claim to be “fish-safe,” there are several concerns associated with their use, and the principal one is the risk of toxic chemicals leaching into your pond and ultimately killing your fish.
PVC liners often contain plasticizers, particularly phthalate esters (PAEs), which can leach into the water over time. These chemicals have been linked to various health issues in fish, including liver toxicity, cell injury and death, oxidative stress, metabolic disorders, endocrine disruption, immunosuppression and genotoxicity – none of which sounds good for a healthy fish pond.
The release of these chemicals into the water can have both immediate and long-term adverse effects on fish health – leaching will often occur very slowly as well as immediately, so it may take several years for the health of your fish to deteriorate, giving you a false sense of assurance regarding your liner choice. To avoid this loss, it’s best to choose the ideal materials for your fish pond liner right from the start, and these will generally be polyethylene and polypropylene materials, which are inherently safe for fish and plant life.
Safety becomes doubly important of course if the fish pond is intended as a source of food or as part of an aquaponics system. PVC liners can be designed and certified for food use, but the question will arise as to the reliability of the certification here.
The gold standard for a fish pond liner is the NSF/ANSI 61 certification from the American National Standards Institute, which indicates the material is suitable for containing drinking water. Check directly with the manufacturer and look for this certification (it’s a higher standard than the US FDA food-safe standard), rather than trusting to a simple labeling of fish safe or food safe.
What’s the Best Choice for a Fish Pond Liner?
For fish and food-safe pond liners, the best materials to look for are generally considered to be Polyethylene-based liners such as HDPE (High-Density Polyethylene) and LDPE (Low-Density Polyethylene). Given the structural requirements of a pond, Reinforced Polyethylene (RPE) sits at the top of the list for a large pond, offering durability, flexibility and fish-safe properties without toxic additives. EPDM (Ethylene Propylene Diene Monomer) is also an option, if reliably sourced and certified.
However, a similar doubt as with PVC can arise with the choice of EDPM for a liner, since there are lower grades of this material used in roofing, and it might be possible to be supplied with an inferior product that will harm the fish. At Western Environmental Liner, while we manufacture more than a dozen different materials, we select RPE for large ponds and RPP (Reinforced Polypropylene) for small ponds. These materials are inherently non-toxic for your fish pond, and give us the rugged qualities needed for a non-leaking and long-lasting pond liner.
Requirements of a Fish Pond Liner
A fish pond liner needs not to leak, so puncture resistance is important, especially as rocks and sharp contours may only arise as the pond is being filled, or after. You want a material that’s flexible and adaptable to pond contours, fitting your topography and landscape design without needing a pre-shaped liner.
You want durability, which means resistance to UV radiation and any chemical exposure that may occur. And while you want flexibility, you don’t want stretching. You want the material to be strong, and yet also as light as possible for the most easy handling. Ideally, you want the pond liner to come in one sheet, custom sized for your pond. Separate sheets can be welded in the field, but the factory is the best place to do this if possible.
If you’re using seaming tape or glue to join sheets of liner material, apply the same scrutiny here as you would to the liner material itself, to make sure you’re not introducing toxic elements into the pond. Opt for welding rather than tape or glue if possible, since any seams are the prime weakness for leakage and faster deterioration.
We have several useful guides to materials and methods for a fish pond and the best liner. You may find these of interest: