In an omega-3-crazed world hungry for fish, Earth's oceans are getting tapped out. So aquaculturists are feverishly farming seafood to meet demand. Seems like a simple solution. But environmentalists complain that farms pollute neighboring waters, concentrate toxins in edible flesh, and disrupt ecosystems whenever a swimmer escapes. Plus, in extreme cases, such as salmon, it takes 6.5 pounds of wild species (mostly plentiful ones like herring and sardine) to grow 1 pound of farmed fish. What's more, some foodstuffs can't be farmed, and with popular entrées like tuna in decline, others are taking up the slack. Hope you like carp.