Here are my thoughts. First of all, the fish are fed fish meal so are not consuming their normal diet. Then fish oil is actually added to their diets to increase their Omega-3 content. This is the “good fat” in salmon that makes it so beneficial to you. In the wild, salmon develop their amazing Omega-3 content by swimming, not by consuming it. Next astaxanthin and canthaxanthin are added to their diets. This is what makes them pink. These are also amazingly healthy, natural substances if you consume them in normal amounts. There has historically been an issue with regulating the amount of these that end up in the fish. Too much canthaxanthin can actually damage the retinas in your eyes. Lastly, farm-raised fish are much more prone to diseases like sea-lice and various viruses. I wonder what they give the fish to avoid these.
I guess the bottom line is that I will continue to watch the progress of farm-raised salmon, but it will take a lot to convince me that anything but natural is best!