Fish is one of the healthiest foods on the planet. However you need to be aware that most fish nowadays contain lots of toxins and heavy metals due to polluted sea, lakes and rivers.

The safest way is wild caught fish.

Aqua culture is more and more common and if you are not sure where the fish comes from you should definitely buy it from there. Just check on how the fish has been fed. Nowadays farms feed the fish with corn and grains which are most likely GMO.