So you recycle, drive a small car, and try to eat organic. But what about running an eco-sustainable fish farm combined with a naturally fertilized vegetable patch in your kitchen?

Christopher Toole and Anya Pozdeeva, two former New York bankers who founded the Society for Aquaponic Values and Education (SAVE), are there to help.

"We call it 'beyond organic,'" Pozdeeva, 39, said.

Aquaponics is a technique with ancient roots for breeding tank fish, recycling their effluent-filled water to fertilize vegetation, then allowing this naturally cleaned water to drip back into the tank below.

It's a perfect, miniature eco system that will let you grow healthy food right in a cramped apartment with almost no specialist equipment.

"We built our system just from trash cans," said Pozdeeva, a slender woman who emigrated from Russia's Siberian region 20 years ago and still speaks English with a gentle accent.

If growing fish to eat in your New York apartment sounds unlikely, then Toole and Pozdeeva are even unlikelier urban eco pioneers.

Just a short time ago they were bankers working crazy hours among the skyscrapers of Manhattan, a far cry from the gritty Bronx where they are based today.

After the 2008 financial crash floored the banking industry, Toole, a vice president at Sovereign Bank, discovered he had a serious eye problem, which he says was stress-related.

And both of them were severely disenchanted with their careers.

"They know how to squeeze every drop out of you and then throw you away," Pozdeeva said.

"We wanted two feet on the ground," said Toole, 47, and striking-looking with a bushy gray beard and pork pie hat.

Instead, he put two feet in the water.

Toole knew a little about fish from childhood summers with his scientist father out at Woods Hole in Massachusetts, a famed marine biology research center in the Cape Cod area. Aquaponics, he reckoned, would let him marry sustainable food production with what he hopes will be an equally sustainable business model.

Risky? Yes.

"But understanding risks is something they teach you a lot about in banking," he said.

Each week Toole and Pozdeeva teach aquaponics to about 80 children at SAVE's base at a community center in the south Bronx, one of the most socio-economically disadvantaged neighborhoods in the United States.

During a recent session, the couple got youngsters to help in everything from cleaning fish tanks to planting mint, cabbage, and other greenery.

The children, more familiar with the Bronx's concrete jungle, were quick to get involved.

"I'm afraid he's going to come up and bite me," a small girl giggled as she put her hand into the top of a barrel containing large tilapia.

"Well, he's afraid you're going to go down and bite him," reasoned Toole.

When two boys turned from gardening duties to a mud fight, Pozdeeva calmly stepped in. "Dirt is precious," she reminded. The boys got back to gardening.

Toole breeds several fish in his trash can farms, but tilapia do best.

They require just five to 10 gallons (19 to 38 liters) of water and by nine months are big enough to eat. Besides, they can be entirely vegetarian and seem to like duck weed, a grainy green plant which Toole and Pozdeeva scoop up from ponds in the Bronx's big Van Cortland Park, then drop into their tanks.

"It's illegal, but on the other hand it's choking the pond, so you could argue we're doing it as a favor," Toole said of the freelance weed harvesting expeditions.

In addition to the teaching, Toole and Pozdeeva sell tiny tilapia fingerlings to customers at $5 a head via their website, Facebook and other sites.

SAVE is barely a year old. But Toole and Pozdeeva clearly have many more fish to fry.

Toole is eyeing partnerships with chefs, other urban fish breeders, and consultancy work for newcomers. But having escaped the banking world, he doesn't want to end up serving a new master, or "selling our soul," as he puts it.

There seems little danger of that.

Pozdeeva has discovered that mushrooms, growing on a simple piece of cardboard, thrive in the same warm, dark, damp conditions that tilapia like. And Toole is excited about branching out into honey production.

"Right now I have 10,000 bees in our living room," he says. "So I'm not just sleeping with fish, but with bees."

In fact, all that could stymie their green revolution, it seems, are New York's notoriously tight rules on pets in apartment buildings.

"We basically need to keep it kind of quiet," Pozdeeva said about their domestic fish colonies. "But that's the good thing about fish."

[Children arrive at a community center in the south Bronx for a session with the Society for Aquaponic Values and Education (SAVE) on April 19. AFP Photo/Emmanuel Dunand]