What you will not find, however, is any soil.

In its place are beds of pea gravel. Pebble-sized granules of gravel fill the six waist-high beds that measure four by eight feet, and are only a foot deep. From these beds grows anything that could grow in dirt, Rittgers says.

But there is a catch -- literally. In the back of the greenhouse, hidden behind a curtain in an almost Oz-like fashion, rests a seething 600-gallon plastic pond, much like an overgrown children's pool.

In it are about 60 full-grown tilapia, a freshwater tropical fish.

Their job is to urinate -- and in doing so, provide hope that a system such as this can feed some of the world's poorest people, particularly in areas where farming is difficult and protein is a hard find.

Rittgers' greenhouse is an aquaponic system -- a method of farming that uses fish to feed and fertilize plants, which in turn filter the water that gets circulated back to the fish. A naturally occurring bacteria in the gravel breaks down the urine in the pond water to provide the plants with nutrition. (The solid waste from the fish is filtered out and removed.)

A need on foreign soil

Rittgers first became involved with aquaponics after a mission trip to Haiti in 2001 with her church, Blacknall Memorial Presbyterian. Since then she has helped install two aquaponic systems in the struggling Caribbean country.

Haiti, one of the world's poorest countries, has been severely deforested. Farming is marginal because most of the topsoil has eroded.

A social worker, Rittgers lives with her best friend, April Perry, who also does mission work in Haiti. Rittgers is a very spiritual person.

"My faith is very important to me," she said. "It's the driving force in my life."

Rittgers and other church members spent 10 days in Haiti and came back determined to do something that might have a more permanent influence on the extreme poverty and malnutrition they witnessed while working in a clinic.

Fellow Blacknall member and missionary David Kolbinsky told her about aquaponics and how it could vastly improve the health of poor farmers.

"It takes a lot of care but if you get the right people that are dedicated to it, it's quite viable and quite fruitful," Kolbinsky said. He had his own system up and running in his yard until a house fire put aquaponics on the back burner. He hopes to get it operating again soon, though.

Rittgers says that in areas where protein malnutrition is prevalent, aquaponics shows great promise. In addition to the increased volume of fruits and vegetables that can be produced, aquaponic systems help the fish grow, as well.

Her greenhouse has been operating for six years, and about two-thirds of the 90 original fish are still alive. The remaining tilapia, which started as fingerlings, are all now more than a foot long.

In addition to the feed Rittgers throws in, they munch on the algae growing on the sides of the tub. They make ideal aquaponic fish, she said, because they have a low oxygen requirement and reach maturity within six months -- meaning they can also be sold if allowed to procreate. (Rittgers controls her population by keeping only male fish.)

Rittgers' system is rigged electronically so that a few times a day a pump lifts the water from the tub into a grid of perforated PVC pipe that waters the gravel beds.

The beds flood a bit, and as the water recedes it collects back into the pipes and is then purged all at once into the pond. It spurts forth from a showerhead-like nozzle at an angle into the water, oxygenating the pond. The tilapia line up to swim against the current and fill their gills.

Hope fades, then floats

The systems Rittgers and others helped install in Haiti are not electrically operated, because power supplies there are unreliable. Instead, the water is pumped by hand up to the beds, and gravity simply returns the filtered water back to the pond.

Rittgers was associated with the installation of aquaponic systems in two Haitian villages through Family Health Ministries, a nonprofit she joined through her church. In the past few years, however, the group has decided to go a different direction, so now Rittgers' work is done mainly through Luke's Mission, a local nonprofit she co-founded with friends.

Keeping up with the systems in Haiti has not been easy, she said, due to a combination of cultural differences and the country's tumultuous political climate. They have lost contact with both villages, though they know both had successful aquaponic systems for at least awhile.

Some people might find developments such as these disheartening, especially since it took a lot of convincing to get the villages' peasant leaders to agree to an installation. And there are countless unforeseen hurdles, as they learned the hard way when one system operator accidentally killed all the fish after giving them the wrong feed.

But Rittgers is hopeful. Her group is installing more aquaponic systems and latrines -- improved sanitation, like improved nutrition, she said, is more than just a "Band-Aid" to the nation's problems.

She just needs people on the ground she can work with, she said.

"I know this works."