WALNUT CREEK -- The city has a new weapon against goose poop in Heather Farm Park's cement pond -- floating islands.

To cut down on chemically treating water and to give fish a chance to thrive, Walnut Creek became the first Bay Area city Tuesday to try out man-made floating islands as an environmentally sustainable way to get cleaner water and improve fish habitat.

Volunteers planted and launched two 100-square-foot "BioHaven Floating Islands" in the park's cement pond Tuesday. Using recycled plastic drinking bottles on the bottom, which look like 12-inch-thick steel wool pads, the islands' tops were loaded with mulch and about 50 plants each. The islands act as wetlands designed to suck up pollutants from the lake floor and at the same time create shade for fish, fostering a new habitat.

"If this works -- and there is no reason why it shouldn't -- the water quality will be substantially cleaner without" chemicals, said Mayor Bob Simmons, who helped plant and launch the islands Tuesday. "It will make the pond look nice, and I think a lot of people will appreciate that."

The islands will be chained to the bottom of the eight-foot-deep lake, so they won't move around too much. They also shouldn't be accessible to people.

Within a year, the islands will be established, and their root systems -- which can grow four feet long -- will suck out pollutants, said Mike Vickers, Walnut Creek's public services manager.

Kids from Seven Hills School, up the road from Heather Farm Park, were the main planters on the islands Tuesday. Made by Floating Islands West based in Mokelumne Hill, the islands have been installed in Los Angeles County, but Heather Farm's are the first municipal installation in the Bay Area, said Laddie Flock, CEO of the company.

Watching the kids learn about the islands, the plants and the fish is exactly why the Diablo Valley Fly Fisherman club wanted to get something done at the lake they use. Club members contacted the city eight months ago to see if the islands were a possibility to improve the fish habitat in the lake. The fish average only about five inches long, said Ted Shapas, conservation chairman with the club. There are bigger fish only after the Department of Fish and Wildlife stock the lake with catfish, bass and trout a few different times of the year.

But fisherman's club members felt creating a better habitat is the right thing to do. And they hope a thriving lake with bigger fish will attract more kids and families to the lake, and eventually result in more fishing, said Dave McCants, a fly tier with the club.

"Kids are not around nature that much, this gets them out here to see there is much more in life than just video games," he said.

The islands' $12,000 cost will be offset by the savings from water chemicals the city will no longer have to buy.

For the first several months, short fences will surround the islands to discourage geese. Once the plants have been established the fences will be removed and wildlife such as birds, insects and frogs should thrive.

If this is successful and cuts down on costs, Simmons thinks more islands could be installed at Heather Farm's natural lake to improve habitat there.

Resident Martina Moser, taking a walk in the park Tuesday, thinks the islands are a great idea. She has caught fish in the lake herself.

"I think it will help clean up the water ... and will definitely make the lake more natural," she said.

Contact Elisabeth Nardi at 925-952-2617. Follow her at Twitter.com/enardi10.