4. Farmed salmon
Similar to apples, many people now consider salmon to be the gold standard in healthy fish no matter where it comes from. Sadly, this is most definitely not the case — all it takes is a single visit to a salmon farm to see just how unhealthy these fish really are.
Farmed salmon are confined to cramped, overcrowded pens and fed a nasty concoction of things which could hardly be called food. These include hydrolyzed chicken feathers and poultry poop, two things which are a far cry from their natural diet and which cause these fish to develop quickly but in a horrifyingly unhealthy manner. The result is salmon meat that is nutritionally devoid, has a much lower omega-3 content than natural salmon, and which often contains residual amounts of the antibiotics and pesticides found in the fish feed.