No one aquatic habitat is quite identical to another, whether you’re comparing them in the wild or in a zoo environment. However, they all share some common requirements when it comes to pond liners. Impermeable liners are necessary for almost all constructed aquatic habitats, whether it’s a wetland out in a housing development or an aquarium feature at a hotel. If the liner isn’t used for the primary enclosure or habitat itself, it’ll likely play a role in secondary containment for spills or for supporting water features like retention ponds and moats. Finding the right pond liner for direct exposure to fish, animals, and drinking water supplies is essential, but even moats and trenches need proper lining too. Here’s what you need to know about selecting pond liner materials for natural and constructed aquatic habitats.
A Question of Fish-Safety
For almost all aquatic habitats, the first concern is general fish-safety. A liner that isn’t rated as safe for fish likely isn’t safe for other marine animals or life either. Regardless of the type of aquarium or enclosure, it’s best to start with a fish-safe liner. Only laboratory testing can confirm a particular liner is truly safe for fish exposure after it's manufactured. Companies that only rely on former testing done on the raw materials can’t guarantee true reliability for sensitive environments or rare species. Stick to providers that back up their safety and compatibility claims with testing. For native and natural restoration in particular, make sure the liner is plant safe as well. Almost all liners that are safe to use with fish will be compatible with plants too, but it’s best to check for both before assuming.
Potable Water Testing
It’s not required that ponds and water features designed for animals to drink from be built with potable water approved liners. However, it is required for human drinking water supplies and recommended for animals as well. Other liners can leach plasticizing chemicals or even lead into the water. Even in very small amounts the exposure can add up over the years, especially in small animals, amphibians, and reptiles that are particularly sensitive to the compounds. For the highest level of safety for sensitive organisms, choose potable water safe liners. BTL liners can meet and exceed your needs in this area as well, ensuring peace of mind when building laboratory enclosures or other highly controlled habitats.
Freshwater vs Saltwater Habitats
Salt can deteriorate many liners, especially in the concentrations found in brackish or tide pools. Habitats simulating these intense environments will need liners that won’t break down upon constant exposure to high salinity. Many of BTL’s products are used specifically for holding concentrated brines produced by wastewater treatment or water desalination plants. These liners can certainly withstand any amount of salinity that would be found in a natural or constructed habitat. Other liners may work well for both saltwater and freshwater use, but it’s best to choose a material tough enough to handle the harshest conditions in the enclosure. This ensures that changing water quality parameters won’t threaten to shorten the lifespan of the liner.
Durable Materials
It’s not just a question of compatibility when choosing a liner material for aquatic habitats. The material must also be strong and durable enough to withstand the weight of soil, concrete, and thousands of pounds of water pressing down on it from above. From below, sharp rocks, roots, and abrasive soil materials express wear and tear constantly starting from installation onward. Choosing a durable liner material is key to all types of aquatic habitat construction and restoration. For the best durability, look for a reinforced material. For example, BTL Liner’s reinforced polyethylene (RPE) is filled with a layer of scrim material that lends to superior tear and rip resistance. Reinforced polypropylene (RPP) is another material option that is tougher and more tear resistant than non-reinforced products.
Why Not PVC?
Polyvinyl chloride (PVC) is commonly used for lining pools and other decorative water features, but it’s far from a good idea for sensitive aquatic habitats. It’s too likely to leach out chemicals like plasticizers to qualify as fish-safe in many cases. Due to its lower durability when compared to other liners, it’s not a good choice for wild habitat restoration where it could spread into the environment as it breaks down. Many PVC liner products aren’t strong enough for buried installation without stretching and tearing, yet the material is also prone to UV damage when used for exposed installation. It’s best to avoid PVC altogether for habitat restoration or creation and stick to other materials instead.
HDPE, LDPE, and RPE
RPE is commonly confused with high density polyethylene (HDPE) and low-density polyethylene (LDPE). As their name suggests, HDPE is a little stiffer and tougher than LDPE. This also makes it less flexible and harder to install. LDPE is flexible and adaptable, but it’s less tough and doesn’t always have the best chemical safety for fish and plants. RPE combines the best of both products, with a reinforcement layer. It’s the ideal material for most aquatic habitat projects thanks to its flexibility, thin construction, high durability, and ease of installation.
Buried vs Exposed Installation
Most aquatic habitats call for buried installation of any liner materials so that they’re hidden from view and kept away from the sharp claws of animals and insects. However, not all liners are built to handle the weight and pressure of buried installation. This is especially true when concrete and rock work is involved over the surface for a more natural appearance and to build specific water features. Exposed installation can reduce the strain on the liner to just the weight of the water, but this creates another risk with UV exposure. Even the best liners tend to last shorter periods between replacement when they’re constantly exposed to the sun. For a product that can handle both types of installation depending on the specific product, try RPE from BTL Liners.
A Question of Underlayment
Depending on the weight pressing down on the liner and the smoothness of the prepared surface below, an RPE liner may still need underlayment to cushion it. Underlayment is a thicker, woven or pressed material similar to felt that functions as a cushion and protective layer for the liner. Installed underneath, it doesn’t hold water back itself but instead keeps the liner from coming in direct contact with soil or concrete. This can greatly extend the lifespan of the liner and prevent leaks if the surface under it is particularly rough or there’s a lot of weight from above.
Don’t let pond liner selection become an overwhelming part of the aquatic habitat design process. Whether you’re restoring an existing wild habitat or building a controlled enclosure from scratch, BTL Liners has the expertise to guide you to the right selection. Talk to one of our team members today about your plans to get custom recommendations on which of our RPE and RPP liners will work best for you.
