Lettuce grown in aquaponic farm in Cocoa, FL. (Courtesy of HealthyLiving Aquaponics)

Consumers associate the word “organic” with healthy and safe, and that sounds simple enough.

But exactly what kind of food should get the U.S. Department of Agriculture's “organic” label has been the subject of repeated controversies, and some of the fiercest divisions have opened recently over the eerily beautiful, scar-free produce that is grown in controlled water-based environments - that is, with the roots of the plants resting in covered water tanks rather than soil.

These methods, valued for their efficiency and reliability, have produced sometimes flawless lettuce and tomatoes that are sold in supermarkets.

But critics say that because these so-called aquaponic and hydroponic systems depend entirely on what humans put into the water, the produce they generate offers less nutritional value than the produce generated by plants grown in rich soil.

“Those heads of lettuce that are grown indoors? Yes, they’re beautiful. But it's just a green leaf with water in it,” said Jeff Moyer, long-time farm director of the Rodale Institute, an organic research outfit. “They can’t possibly have the vitamins and minerals that lettuce grown in soil would have.”

So far, despite the objections of its organic advisory board, the USDA has decided that the produce generated by such systems is worthy of the valuable organic label, as long as the other organic guidelines are followed. The designation allows the farmers to charge a premium of as much as 30 percent or more.

The debate over aquaponics and hydroponics is one front in much broader war over what may be sold as “organic.”

On Friday, the Cornucopia Institute, a nonprofit group representing some farmers and other interests, called for the resignation of the chief of the USDA’s National Organic Program, citing the aquaponics decision and other issues. The focus of Cornucopia’s discontent is the way in which the USDA has, in their view, ignored the recommendations of the organic advisory board, a 15-member panel created by Congress to help shape the organic rules. Board members and USDA officials have also differed on an array of topics including how animals should be treated and what kinds of synthetic materials may be added to organic products.

The contest has often split the organic world into multiple camps, sometimes pitting smaller outfits against larger, more corporate entities. "Although the USDA ignored some of the [board] recommendations in the past, until recently they never went 180 degrees in the opposite direction in deference to the preferences of powerful corporate interests," Kevin Engelbert, a former board member from Nichols, New York said in a statement.

A spokesman for the USDA noted that the government is convening a special task force to reconsider the water-based systems. "Emerging technologies in hydroponic and aquaponic production have prompted [the USDA] to seek the most current information and opinions of industry experts," the department said.

Hydroponics, or growing plants in a nutrient solution root medium, is a growing area of commercial food production, with more than $500 million in annual revenues, with the best-sellers being tomatoes and lettuce, according to market analysis by IBISWorld. Since 2002, a few dozen such operations have obtained the USDA organic certification, according to government figures.

Defenders of the aquaponics contend that  the produce they generate is nutritionally equivalent and moreover, cleaner.

Al Eisler, owner of an aquaponic farm in Cocoa, Florida grows lettuce, spices and tomatoes in water tanks inhabited by tilapia. The only things he adds to the water, he says, are organic fish food and, occasionally, some minerals.

The plants mainly feed off of the wastes generated by the fish.

“It’s a natural cycle,” Eisler said. “It’s what happens in rivers and ponds.”

Besides, he said, he has an incentive not to cheat by adding chemicals, as some other farmers may.

“The fish don’t lie - if we cheat, they die,” he said. “That’s our motto.”