The open-net salmon farms that dot B.C.'s coastal water are spreading sea lice to wild stocks. But the alternative, land-based tanks, are too costly to operate at a commercial level.

A Campbell River aquaculture company may have found the happy medium that can make salmon farming sustainable and profitable: big floating tanks.

Agrimarine Industries is currently building a large tank, made of high-density foam and fiberglass, that will float in the waters of Middle Bay, off the southeast coast of Vancouver Island. The project is a compromise between land-based systems, which completely isolate farmed fish from the marine environment, and open-net marine systems, said director of operations Rob Walker.

Agrimarine did operate a land-based closed containment system in Cedar until 2005, but the technology was too expensive to be commercially viable, said Walker.

"At Cedar we were pumping uphill all the time with 75-horsepower motors," he said. "The whole closed system is very expensive, it requires high capital outlay and high maintenance and operations costs as well."

Walker said this technology allows water to flow through but captures waste and disposes of it on land. He said it "doesn't directly address the issue of sea lice," but will attempt to avoid infection by drawing water from deep down if necessary -- sea lice tend to congregate near the surface of the ocean.

Corey Peet, aquaculture specialist with the David Suzuki Foundation, said this approach to salmon farming is "definitely a good step forward, but we will have to see what the results are."

"In theory it's the right idea. I think it is likely a happy medium between land-based and open-net systems," he said. "If and when we find have a good solid example of sustainable farmed production, I think it's going to get a lot of support from NGOs."

The first tank -- which is 24 meters across and holds 3,000 cubic meters of water -- will likely be launched this July with at least four more tanks to follow, said Walker.

Colleen Kimmett is a Vancouver-based journalist who writes about science and the environment.