Whether you love the elegance of Japanese koi or dream of raising edible tilapia in your own backyard, a simple lined pond lets you experiment with the world of aquaculture. However, using the wrong type of rubber sheeting for lining your pond could ruin your plans and cost you hundreds or even thousands of dollars in lost fish. Find out how to pick the perfect liner for your fish rearing pond and why liner composition matters to these delicate underwater creatures.

What's Dangerous About Some Liners?

When you're designing a pond that will only hold water and not plants and fish that are sensitive to chemicals, it's not that important what chemicals leech out of the liner material due to years of daily exposure to sun and water. Add fish to the pond, even relatively tough species like catfish, and it suddenly matters what chemicals the fish are absorbing with each new flush of water over their gills. Fish are very sensitive to the chemicals that can leech from plastic and rubber pond liners, so it's essential to only build ponds with approved and tested liners.

Is EPDM a Good Choice?

Ethylene propylene diene monomer rubber (EPDM) is one of the most commonly used materials for sheets because it's tough, stretchy, and easy to manufacture. It's one of the most common and popular pond liners, but the exact same sheets are also used in construction as a water barrier for roofing and exterior walls. While some EPDM products are perfectly safe for ponds containing fish, it's very easy for a shopper or a supplier to accidentally sell construction grade rubber as a pond lining material.

Why does it matter whether you're using roofing or pond liner in your pond? Unfortunately, EPDM sheets that aren't made specifically for use with fish and aquatic plants are made with a wide range of chemicals that plasticize and strengthen the material. Since these sheets are designed for your home instead of a pond, they're not specifically tested to see what leeches out during long-term water exposure. On top of that, most non-pond EPDM products contain additives to prevent mold and algae growth, two common sources of roof damage. Those algaecides and fungicides are not tested or approved for use with fish, especially fish you plan to consume in the future.

How Does PVC Liner Stack Up?

Aside from EPDM liners, many pond owners also consider PVC sheets. These plastic liners are a common source of arsenic that leeches into water over time, so it's essential to also make sure that any PVC products are designed and tested to be safe for fish. Aside from being a potential source of toxins, PVC has other limiting features as a pond liner, like the following:

• Faster breakdown when exposed to UV rays from the sun, especially along the edges of a pond
• Less stretching ability to cope with changes under the liner due to growing tree roots or eroding soil
• More likely to spring a leak along sealed seams where cuts were necessary to create a curve or shelf.

How Can a Fish Owner Find the Right Liner?

Since every major material used as a pond liner could potentially contain dangerous toxins, it's best to stick only to products that have been tested and guaranteed either by the retailer or manufacturer. Without long-term tests in the real world to check water quality and safety, you're always gambling with the health of your fish.

What Pond Liners Should Be Avoided for Fish?

Aside from choosing a fish-safe PVC or EPDM liner product, you should also steer clear of butyl rubber formulas altogether. Aside from being expensive and very difficult to work with, they're known for leeching out high levels of toxins over long periods of time. There's no reason to deal with toxic ingredients, installation difficulties, and high prices all at once.

For more information and options, talk with local businesses that supply pond liners, such as Billboard Tarps.