> Fish farms are in a unique position because unlike farming animals on land, it can be done without radically changing the part of the ocean the fish are farmed in.

Fish farms are a little like farming rabbits in packed, huge fenced in areas.

You get a lot of disease, use a lot of medicine and antibiotics - and get a lot of feces. And escaped, diseased rabbits that breed in the wild.

Fish farms on land are likely better - but at any rate, fish farms are far from being without environmental impact.