Don’t underestimate the number of options you have for lining a nursery pond, even after you decide you want a flexible geomembrane. Your options include:
- Polyvinyl chloride (PVC)
- High density polyethylene (HDPE)
- Low density polyethylene (LDPE)
- Ethylene propylene diene monomer rubber (EDPM)
- Reinforced polyethylene (RPE)
Ornamental vs Food Fish
Both ornamental and edible fish require a fish-safe liner that won’t release any chemicals that harm the fish or slow their growth. However, edible fish nursery ponds must go a step further and only rely on food-safe liners as well. Thankfully, most fish-safe liners are also rated for food use in aquaponics and aquaculture settings. Check with the manufacturer to verify the ratings and certifications of a particular liner product before ordering it for your nursery pond. If you need help, call us here at BTL Liners and we’ll guide your selection based on the final use of the mature fish.
Fish-Safe Liner Products
Geomembranes are often called pond liners, but not all flexible rubber or plastic materials are safe for growing fish. Fry are particularly sensitive to chemicals known as plasticizers that keep the liner flexible and resistant to cracking and tearing. However, some fish-safe liners offer plenty of crack resistance and flexibility without any toxic additives. Reinforced polyethylene (RPE), high density polyethylene (HDPE), and low density polyethylene (LDPE) liners are all good options with fish-safe formulas that are still highly durable. NSF certified pond liners are both fish-safe and food-safe, making them ideal for raising edible fish fry. The same liner can be used for all stages of rearing ponds for stable environments that are easily maintained.
Flexible vs Poured Liner Options
Flexible liners, especially reinforced materials, are capable of conforming to fit most nursery pond designs. Don’t assume that gently sloping sides or tight corners necessitate the use of a poured liner. Poured in place liners like concrete will conform to nearly any design, but they’ll slump out of steep and overhanging edges without reinforcement and forms. Flexible liners are far easier to adapt to difficult areas than poured in place options. With anchoring points and attachment options for rebar driven into the ground, there’s no shortage of options for customizing a flexible nursery pond liner.
PVC was one of the first flexible pond liners to arrive on the market. However, it’s far from your best option today. PVC is highly flexible and offers lots of custom design options for a long and narrow or unusually deep nursery pond. Unless designed specifically for fish and food use, PVC liners tend to include plasticizers that hurt fry. Arsenic is a common contaminant found in pond liners that aren’t strictly tested for fish compatibility. This material also isn’t UV resistant, requiring you to leave a foot or more of soil over it each time you clean to remove sludge. This eliminates the easy cleaning routine promised by other flexible geomembranes.
HDPE and LDPE
If you’re looking for an affordable product that is fish-safe and often offers food safe certification as well, consider HDPE or LDPE liners. The best products combine both of the materials in multiple layers to create a liner with advanced UV resistance, flexibility, and crack resistance in cold weather. Composite liners also save you money by stretching more expensive materials with less expensive additions. AquaArmor from BTL Liners is a great example of an HDPE and LDPE product that is fish-safe and ready to use for nursery ponds.
This material is the thick, flexible sheet rubber many people are familiar with from roofing membrane purposes. EDPM is fish and plant safe, but many formulas are not considered food safe. This material requires seam tape sealing methods that are more prone to leaking than heat sealing. The thickness and high weight of this liner makes it hard to mold around unusual features and slows down the installation process. EDPM can work as an insulating liner for nursery ponds in cold climates, but otherwise it’s far from an ideal material for this purpose.
Polyethylene is a fish-safe material that is tough, flexible, and UV resistance. When you add in a reinforced mesh embedded in the liner, you’ve got the best choice for lining your nursery pond. These liners offer the same strength and tear resistance of EDPM and PVC at half the thickness, dramatically reducing the total weight and speeding up installation. Despite the relatively thin design, this material is highly resistant to punctures and tears. If you miss a few rocks or roots during preparation for the new pond, you won’t have to worry about leaks. An RPE pond liner can last upwards of 40 years with proper maintenance.
You don’t have to make the choice of a pond liner for a nursery setup all on your own. BTL Liners is happy to help with the selection. If you’re looking for a fish safe and food safe liner product, check out our selection or contact us for advice tailored to your particular hatching and rearing system.