Building better ponds: five easy steps for turning a rubber or concrete pond installation into a work of art—rather than a master disaster - Quarterly Market Report

Pool & Spa News, March 27, 2004 by Janice Rhoshalle Littlejohn

"Back in the early '80s, we used a blue swimming pool liner for the first water garden we built, and we introduced fish," remembers Dietter, president of Dietter's Water Gardens in North Haven, Conn. "All of the fish died within 24 hours."

The culprit, he learned, was in the manufacturing of the liners. Chlorine and other chemical gases leached from the liner and were toxic to the fish.

In recent years, with the popularity of rubber liners, some roofing manufacturers have started developing liners for the pond industry. They claim these liners are suitable for aquatic animal life, koi and goldfish.

"Then we had a situation just last year, where a manufacturer got a batch of roofing rubber mixed in with pond rubber," Dietter says. "And it killed all the fish once again."

After that incident, he began doing his homework. "For years, the liner manufacturers have talked about being fish-safe," Dietter says, "and the theory in the industry was, 'Yeah, sure, they're going to say that because they're going to charge more for it.' But this past year was a perfect example that there is a difference between roofing rubber and pond rubber."

The difference is in the curing process. While various chemicals and raw materials are used for roofing liners, fish-safe liners are made of a consistent raw material composite, which makes it watertight and fish-friendly. All fish-safe liners have to be certified with the Environmental Protection Agency seal.

Fish-friendly liners may not necessarily be wallet-friendly, but Dietter cautions against pinching pennies with low-priced roofing liners. Ultimately, you will pay for it later when you have to replace the liner, add more fish or face a lawsuit from an angry pond owner.

"One of the reasons it may be a little more expensive is because they use the same ingredients even if they're a little more [costly]," Dietter says. "They know combining these raw materials will make the liner 100 percent fish-safe:'

Interestingly, most people don't decide that they want fish in their ponds until months or even years after they've built them. But Dietter believes it's not always necessary to replace the liner if you're dealing with a reputable pond supplier.

"Most builders are using fish-safe water garden materials to begin with," he says. "So as long as you're buying from someone in the water gardening business, rather than a roofing manufacturer, you should be safe."

--J.R.L.