Healthy Water: Healthy Fish
When making a home for fish that you want to keep around a while, providing a safe environment should be your primary concern. Fish grown in healthy, safe water will mature faster and develop better than those exposed to toxins or lacking necessary nutrients. There are lots of factors to consider when building an aquatic habitat, but the choice and quality of materials you use are an essential piece. These elements include filters, pumps, and liners. Regardless of the aquarium or enclosure, a fish-safe liner is essential.
Pond liners are used to contain the water the fish live in, breathe, and essentially drink. Low quality liners, that leak plasticizers or other chemicals into the water, present significant health risks both for long-lived koi and small ornamental fish. Not only will chemicals harm your fish over time, but they can also negatively affect plants, smaller critters, and other essential parts of the ecosystem necessary for a healthy, beautiful habitat.
Most ornamental fish are not as long-lived as Koi, but they can be more susceptible in the short term to even small amounts of toxins since they tend to be smaller than their cousins. Fish deaths in a newly lined pond may be easily attributable to toxic coatings designed to inhibit the growth of algae and fungus on the liner material. Using a process of elimination, it’s possible to identify (but expensive to fix) the culprit, while longer term toxic exposure is often a real puzzle. Just because your koi didn’t expire within the first week of introducing them to your EPDM-lined pond doesn’t mean that there are no dangerous toxins gradually leaching into the water. Regular water changes can slow (but not eliminate) the gradual buildup of toxicity, so five years down the line, respiratory distress, failure to eat, tumors, or apparently sudden death arising from a slow accumulation of toxins isn’t so easily traced to a poor choice of liner. Be cautious of this - fish enthusiasts will often reason that their EPDM roof liner pond didn’t have any deaths in the first 2 years, so the liner must be safe, and they may recommend it enthusiastically as a cheaper alternative to higher priced liners. Yet, long term damage to your beloved fish is rarely justified by a quick and easy price advantage.
The ideal liner for a koi pond does not employ plasticizers or other dangerous toxins. It’s also durable and resistant to damage from frequent draining, regular maintenance, UV exposure, or outside disruption.
When “Fish-Safe” Isn’t Safe for Your Fish
Traditional liners for backyard ponds include Polyvinyl Chloride (PVC), Ethylene Propylene Diene Monomer (EPDM), High Density Polyethylene (HDPE) and Reinforced Polyethylene (RPE). Each type of liner has functional advantages and disadvantages, but even those liners marked as “fish-safe” may be questionable, since there is no industry standard and each manufacturer chooses whether to use that designation.
Certain liner materials pose risks to health if allowed to come into contact with your fish. PVC, in particular, often contains plasticizing chemicals that aren’t approved for long-term exposure by humans or animals. An unsafe liner can lead to dangerous effects later down the line, either individually or on a widespread level. While PVC (polyvinyl chloride) is widely used today, it also comes in many forms. Rigid PVC, such as piping and plumbing, does not contain plasticizers and is certified as food safe. There are other PVC materials, though, that definitely are not fish safe. When you’re considering liners for your ponds, it’s important to remember that flexible PVC usually contains phthalates or BPA, used to keep the naturally brittle material pliable and flexible, suitable for lining a pond. Other materials used for liners and sheet goods may contain hydrogen chloride and dioxins, which can cause severe respiratory ailments, birth defects and cancer in humans when exposed to potable drinking water sources. It’s safe to assume that such hazardous toxins are likely to harm your fish as well.
Durable, leach and chemical resistant, and food-safe liners are the best way to ensure safety. Since the designation of fish-safe is not based on specific, tested qualities, the safest option for your fishpond is to use NSF-61 certified (potable-water certified) liner. BTL offers a range of durable, puncture and tear resistant RPE liners that are NSF/ANSI - 61 certified for food preparation and for storing drinking water, the highest safety designation available.
