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Ecodur 201: Coating an Ornamental Fish Pond


Ornamental fish, especially those in ponds where the public can enjoy them, are big business, especially large koi, the jewel of the carp family. In a well balanced watery environment they can live for a very long time and prime specimens can command eye-watering prices, although typically they will run from $15 up to around $5,000.

This case study concerns a small North Carolina residential pond where the original liner coating was killing fish and leaking. Today, EPDM, RPE, rubber and butyl liner products are commonly used and some pond owners have even used PVC with dire results from off-gassing of plasticiser compounds. A completely non-toxic environment with the correct PH levels for fish and other aquatic life is paramount if they are to thrive and breed successfully.

In many instances, aquatic life can be far more vulnerable to many compounds that humans are routinely exposed to with fire retardants, glues and PVC off-gassing being a prime example – the new car smell for instance.


Here the client wanted a lining product that was as natural as possible with zero potential toxicity over the lifetime of the pond. They also wanted zero VOCs and ultra-low maintenance. Some pond liners and coatings can deteriorate from UV at exposed edges. Some also can become brittle and the mere act of moving around ornamental stones can lead to cracks and ultimately leakage.


Castagra’s Ecodur is made from renewable castor oil and naturally occurring soft rock gypsum which is widely mined in the US. It is essentially becomes a plasticised gypsum upon application, sharing a combination of qualities from the original two main constituents. It is permanently flexible, highly robust and chemically neutral.

Ecodur produces no VOCs and can be repaired throughout the coating’s lifetime as new Ecodur will economically bond to original Ecodur. It is also extremely durable against the effects of UV and saltwater tests have shown no measurable deterioration after over 20 years. The ultimate proof of its suitability for aquatic life is that is has an ANSI/NSF-61 rating for contact with human drinking water.

Application Results

As with any coating job, surface preparation is very important. The surfaces must be clean, dry and free of any potential for future flaking. Ecodur, because it has exceptional surface grip, often double that of conventional epoxy coating, it does not require quite the level of surface prep that most of the competition requires. It has excellent penetration of cracks and small holes that further enhances it as a choice for industrial scale water and wastewater applications.

Within 30 minutes of being manually applied to a depth averaging between 30-40 mil, the surfaces were tacky free and full cure was achieved within 24 hours, allowing the pond to be brought back to full use.

Subsequently, it was reported that the pond’s integrity was 100% with no detectable leakages.
The coating application was performed by Heritage Water Systems in January, 2018. Prevailing conditions included dry conditions in the 40 degrees Fahrenheit range. After conditioning, the water quality was deemed to be ready to receive fish at the end of March.