The cultivation of fish, shellfish or aquatic plants (such as seaweed) in natural or controlled marine or freshwater environments. Even though aquaculture began eons ago with the ancient Greeks, it wasn't until the 1980s that the practice finally began to expand rapidly. Aquaculture "farms" take on a variety of forms including huge tanks, freshwater ponds, and shallow- or deep-water marine environments. Today, the farming and harvesting of fish and shellfish is a multimillion-dollar business. Among the most popular denizens of the deep that are farmed are bivalves like oysters, clams and mussels; crustaceans like crayfish, lobsters and shrimp; and fish like catfish, salmon, trout and tilapia. See also hydroponics.