It’s easy to look at a preformed pond and believe it to be sturdy enough to do the job. After all, it’s made of a hard, rigid material and designed to withstand the elements. However, its rigidity makes it more susceptible to problems, especially in cold weather.
Durability
A preformed pond, in fact, is not more durable than most flexible liners. Flexible liners that are properly installed will last much longer. In cold climates, cracks can occur in a small, preformed pond that freezes solid, as well as, in one where the ground freezes and causes upheaval. Many flexible liners are cold crack resistant and are not affected by the same freezing weather conditions that cause cracking in a preformed pond.
Size and Weight
Size and weight can become a problem for preformed ponds, and the larger the pond, the bigger the problem. Large, preformed liners are unwieldy to transport and install, even requiring machinery to do the heavy lifting. A flexible liner, on the other hand, is easily folded into sections, making shipment and installation easier. Additionally, an RPE (reinforced polyethylene) liner such as AquaArmor weighs substantially less, resulting in reduced shipping costs and less effort during installation – even easier than other flexible liners which are heavier.
Fish and Chemical Leaching
Fish are especially sensitive to chemicals used in the manufacture of liners, both preformed and flexible. Although most preformed pond liners are marketed as fish safe, many manufacturers of preformed pond liners, both fiberglass and plastic, fail to perform proper testing to verify these claims. If your goal is to build a pond that is fish safe, look for NSF certification to ensure that the liner has been thoroughly tested for chemical leaching. Some flexible liners, such as BTL Liner’s AquaArmor, are fabricated to be fish and even potable water safe.
Conclusion
Even though preformed ponds are often made with some of the same materials as flexible liners, preformed ponds just don’t provide the same benefits. Plus, when choosing a flexible liner, you have many more material choices, including the multi-layered RPE liner which combines the advantage of several materials to create a comparatively lighter liner that is freeze resistant, fish and plant safe, UV resistant and will not easily puncture or tear.
