Vegetables grown through aquaponics—a combination of fish farming (aquaculture) and plant cultivation without soil (hydroponics)—may be coming to a marketplace near you. Practiced by the ancient Chinese and by the Aztec, the ever evolving technique is going commercial in Europe, Canada, and the U.S. It’s being eyed as a sustainable farming option well suited to cities, islands, and developing regions where water and land are in short supply.