It’s clear that flexible liners have an important role to play in the modern hatchery, whether it’s for lining a ditch to prevent runoff from ruining water quality or for protecting an in-ground pond. Yet, it’s not as easy as just picking a random pond liner and adding it as soon as possible. Installing the wrong liner could hurt the fish fry and fingerlings more than helping them. Some liners are fish safe, but they’re just not the best choice for the challenging environment of a hatchery. This is particularly true for cold water and saltwater operations that are harsh on all the materials used in the facilities. Make sure you’re matching the right flexible pond liner to the job with these tips for fish hatchery selection.
Fish Safety
Fish safety is most crucial aspect of liner selection. Liners that aren’t safe for long-term fish exposure, simply shouldn’t be used in a facility for hatching fish, even if it’s only for containment of spills or for drainage areas. The chance of backflow carrying the unsafe chemicals along to the fishponds or tanks makes it too risky, when there are plenty of fish-safe materials available for all liner purposes. Don’t just settle for liners that claim to be safe for fish and food uses without any testing to back it up. Third party testing, to show the liner material won’t leach out any contaminants, is a needed, along with NSF certifications for food, fish, or potable water safety. Any liners approved for food or potable water use will be more than safe enough for hatchery use.
Food Approval
Speaking of food safe liners, any fish hatched for eventual consumption will likely need a liner rated by the NSF for the intended use. Check with state and federal regulations, from the USDA and FDA, to make sure you’re following all applicable laws regarding aquaculture for human consumption. Fish grown for feed purposes generally aren’t regulated the same way, so fish safe liners will be sufficient for those stocks. There’s no special benefit to choosing food safe liners for ornamental or sports fish, even those that are eaten by some anglers. Sports fish, like trout, typically spend far more time in their final pond or creek environment than in the hatchery where they’re exposed to artificial liners. If the fish isn’t being raised up to the harvest point in the lined ponds, it likely doesn’t need a food safe liner. However, check on all relevant local regulations before assuming that this is true for your particular hatchery.
Material Options
Not all fish-safe liners offer the same benefits to the hatchery owner. Each specific polymer has its own set of strengths and weaknesses. Some are great liners but just aren’t suited to the specifics of a hatchery, while others aren’t suitable for fish at all. Here’s a round-up of the materials most commonly used for pond liners and how they stack up against each other for fish hatchery use.
Best: RPE
Reinforced polyethylene (RPE) is the best choice for a fish hatchery. Its long list of benefits includes:
- A reinforcement scrim grid to increase the tear and puncture resistance of the material while helping it lay flatter with fewer wrinkles
- Custom fabrication options to cover large areas with a seamless piece of liner
- High dimensional stability to help the liner resist the forces of the water pressing down on it for years to come
- Thinner and lighter than other liner materials, lowering shipping and installation costs
- Fish-safe formulations are guaranteed not to harm your fish or interfere with water quality
- Combination of multiple polyethylene materials ensures both high flexibility and durability in one product
Acceptable: CSPE, HDPE, LDPE
All other forms of polyethylene liners, including Chlorosulfonated polyethylene (CSPE), high-density polyethylene (HDPE), and low-density polyethylene (LDPE), are less than ideal for use in a fish hatchery. Each one has a different drawback:
- CSPE: It’s potable water safe and highly UV resistant, but this makes it valuable enough to use as a floating cover. It’s usually too expensive to feasibly use as a liner for large hatchery ponds or tanks.
- HDPE: The material is highly durable and usually fish safe, but it’s slightly too stiff to conform well to unusually shaped ponds and raceways. It’s not the most puncture resistant material either, especially if you choose a non-reinforced material.
- LDPE: It’s more flexible than HDPE, but at the cost of durability. It also tends to suffer more from being unsafe for fish, due to the addition of plasticizers to make it flexible enough to compete with PVC. LDPE liners can crack in the cold as well, which is a problem in cold water and some saltwater hatchery operations.
Avoid: PVC, EPDM
You’ll commonly see the thick rubber material known as EPDM recommended for fishponds. It is fish-safe, but that’s the only benefit it has to offer for a fishpond. This material is very thick and heavy compared to other modern liners like RPE. It’s not puncture resistant at all, leading most EPDM lined ponds to develop leaks after just a few years. Polyvinyl chloride (PVC) is another common liner material that is rarely fish safe. It simply requires too many plasticizing and UV reflective chemicals that leach into the water. Avoid both of these materials for any fish hatchery structures in need of lining.
What About Underlayment?
Most flexible liner materials require a liner if you want them to last more than a few years. RPE is unique because its reinforced design allows it to be installed directly over compacted soil without an underlayment. However, these thick layers of felt-like material are still recommended in some instances. An underlayment acts like a cushion to help the liner above stretch and bend without snagging on anything rough or sharp in the soil. A layer of underlayment adds to the total cost of the project, but it may be less expensive than trying to perfectly smooth and grade the soil. It’s also very helpful when working with slopes that are hard to line without penetrating the material. The underlayment is thicker and heavier, allowing it to cling to the surface of the soil and then it provides something for the liner to grip against as well.
Installation Concerns
Flexible liners are easy to install, but that doesn’t mean they can go on without proper preparations. First, start with careful pond grading and soil preparation. You don’t need to compact the soil as much as you would for an unlined pond, but you do need a smooth and rock-free surface to work with. A lot of cracks and leaks can develop small worn spots that occur when the liner is dragged over a rough and uneven ground. Next, make sure you have enough equipment on hand to transport and install the liner. Most of the unfolding has to be done by hand, but it’s not possible to get the rolls in place or started without help for the largest ponds.
Combining Concrete and Flexible Liners
There’s no need to choose between concrete or flexible liners for a hatchery pond. The two materials work well together and help fill in the gaps of what’s missing from each material. Concrete is better at providing structure and reinforcement to a pond, while the liner actually handles the real work of holding back the water. Existing concrete ponds or raceways in need of lining should be drained, cleaned, and then covered with an appropriate adhesive. This will hold the liner in place against vertical walls and in tight corners. The same process is used for attaching the liner to the inside of new construction, but often the liner is installed under the concrete instead to eliminate the need for adhesives entirely. This also protects the liner from direct UV or water exposure and can greatly expand its lifespan. However, check with the manufacturer to make sure a particular liner is designed for buried installation and contact with concrete before using it in this way.
Using Liners for Containment Around Tanks
If you choose to use any above-ground tanks as part of your hatchery, make sure you’re designing proper spill containment for them as well. Allowing a leak or spill to flood the facility is a waste when it’s easy to create a sloped basin floor and to cover it with an impermeable liner. The same liners you use to protect your outdoor production ponds can double as containment liners both indoors and out. While containment is not usually required by state or federal law at fish hatcheries, it’s still a good idea to keep diseases from spreading and to protect the structures from damage.
On Demand Manufacturing
For the best results from fish hatchery liners, look for manufacturers that offer custom orders. On-demand manufacturing (ODM) for pond liner means you can likely get a completely seamless drop-in panel, at least for ponds below a certain size limit. If you can’t get a seamless panel, you can at least work with the manufacturers to minimize seams as much as possible. There’s no need to settle for rolls that are only a few dozen feet wide when you’re trying to cover a large round or rectangular shape.
It’s a commitment to find the right liner for a fish hatchery, but it’s worth the effort. Still not sure which liner is right for your project? Contact us here at BTL Liners to talk with one of our expert team members. We can guide you through the liner selection process and make sure you’re getting the right materials for a delicate operation like raising fry.
