CHICAGO—They call this place the Back of the Yards, a neighborhood in the middle of the city once filled with acres and acres of stockyards.

In their heyday, those stockyards gave Chicago a reputation as the world's meat-packing capital -- but also as an environmental and health horror brought to life in the stark images of Upton Sinclair's novel "The Jungle."

A few remnants of that industry remain here today. But the stockyards are long gone, replaced by an industrial park and a mindset that, from now on, Chicago will try to move past those images.

Now, you will find a jungle of a very different kind here.

It's on the third floor of an old meat-packing plant, a humid hothouse, of sorts, filled with rows of greens and sprouts, even exotic white strawberries. Nearby, in large blue barrels, lurk tilapia, fish native to tropical regions.

It's all part of the fledgling world of urban "aquaponics," vertical farms set up in old warehouses, where plants and fish are raised symbiotically. The idea is that water containing fish excrement is used to feed and fertilize the plants, which then filter that water before it goes, through a series of pipes, back to the fish.

"I never really saw myself going into farming -- but this was an opportunity to try something different," says Mario Spatafora, a 24-year-old, spectacle-wearing accountant by training who is vice president of finances at this new Back of the Yards company, known as 312 Aquaponics. The company hopes it will soon be selling fish and vegetable greens to restaurants and at farmer's markets in the Chicago area.

It started when one of Spatafora's childhood friends, now one of four young partners in the business, set up a successful aquaponics system in his apartment when they were in college -- and a business idea sprouted.

"I knew that even in the worst case scenario, if we couldn't make this work," Spatafora says, "a tax job and being an accountant would always be there."

But this was their chance to be young pioneers.

Those in the field say interest in aquaponics has been growing in the last three years -- though mostly on a smaller scale with people who have backyard greenhouses or who live in warmer climates such as Hawaii.

Sylvia Bernstein, vice chairman of the newly formed Aquaponics Association, has seen the spike in interest. She started an online community forum for aquaponics gardeners two years ago. Last February, the site had 800 members. This year, there are about 4,500.