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How to create a natural-looking pond with a geomembrane liner

News | September 27, 2021 | By:

Constructing water pond with a geomembrane in Sweden. Photograph courtesy of BTL Liners

Not all lining material is created equal. Although preshaped rigid liners exist, they are not normally what you would choose for your fish-stocking pond. No matter how small or large the pond you have in mind, your best option today is flexible lining material.

Although there are a wide range of options, there are some flexible lining choices that you should avoid, if possible, and others that you should immediately eliminate. These include:

  • Ethylene-propylene-diene monomer (EDPM) material can allow harmful chemicals to leach out and poison fish and plants. EDPM lining is primarily intended for use on roofs and in other situations where it would be covered by another layer of material. In ponds, even if it is deemed fish-safe, it tends to break down from UV exposure.
  • Polyvinyl chloride (PVC) is affordable and flexible, but it also can contain toxic plasticizers and is not recommended.
  • Chemicals used on anti-fungal or anti-algae linings can be damaging to fish, and they also reduce the existence of natural nutrition necessary to nourish young fish.
  • Repurposed tarps can provide a barrier between pond water and the dirt below, but they do not offer an impermeable barrier, cannot be sufficiently sealed at the seams and are frequently of uncertain background. They are an imperfect choice and should be rejected, based on the possibility that they might be a potential source of toxins in the pond.
  • Concrete or spray-on forming material, without a flexible liner to eliminate or minimize seepage through the shell is not recommended.

Working with modern lining material is not difficult. BTL Liners fabricates geomembrane liners to cover the bottom and sides of any pond you wish to create. Our expert team will assist you by offering advice, price quotations, technical assistance and even installation, so that the result will meet your exact requirements.

Relative advantages of HDPE, RPE and LLDPE

Flexible liners of these three materials are all fish-safe and extremely durable. Tear resistance is of concern, because all fishponds must be cleaned periodically. All liner materials will tend to become brittle over time, and cleaning vacuums and nets used to remove sludge can damage liner surfaces. Durable, UV-resistant liners boast a life span that can be double that expected from most other lining materials.

Both high-density polyethylene (HDPE) and reinforced polyethylene (RPE) have high tear resistance, but HDPE is heavier and more difficult to install. It also has lower UV resistance than either RPE or linear low-density polyethylene (LLDPE). On the other hand, LLDPE offers high UV resistance, but can be more prone to tears in certain conditions. Thus, RPE is typically the best choice. It combines the benefits of both HDPE and LLDPE into one liner, with the added benefit of a strong reinforcement layer.

Although the ultimate decision will be based on several variables, you should also consider the difficulty involved in sealing the seams to create a watertight installation. For a small fishpond, you could opt to have a liner fabricated with factory-welded seams. If, however, the seams must be sealed on-site, each of the three recommended BTL liners can undergo heat-sealed seaming that will not loosen, even after years of underwater use. Additionally, they will not contribute to any leaching of harmful chemicals into the water supply.

Once the liner is installed, you have a blank canvas ready to receive the water, plants and fish you have planned.

Naturalizing your pond

When your pond setup is complete, you can begin to focus on adding the trees, shrubbery and plants that will enhance your border. Your goal should be to “naturalize” the appearance rather than to “landscape” the perimeter of the pond. Feel free to add plants in the dirt near the edge of the pond or to place aquatic plants in pots in the water. Add varieties of vegetation that will thrive in water and that will add depth to the watery environment. Water lilies are a great choice because they offer shade and hiding places for fish. Your edge plantings will help maintain water quality and discourage algae. Be sure to avoid invasive plants that will overgrow your pond surface.

Use bricks, river rocks, flagstone, slate or natural hardscape found in your locale to add interest to the pond perimeter, or place then on the sloping sides of the pond, either below or at the waterline. Avoid using sand or pea gravel, because they make it much more difficult to perform the necessary seasonal cleaning tasks and pond maintenance.

This article first appeared on the BTL Liners blog,

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