Farmed fish spend their lives in overcrowded and filthy enclosures (too much fish defecating and feeding in the same cubic meters of water). Their feed is ridden with chemicals and antibiotics.

It's the same issue as "normal" poultry vs "aviary" poultry.

I personally prefer to eat less fish and meat than eating animals that are bred and raised in awful conditions that optimize for revenue; the quality of the output speaks for itself.

- https://www.scientificamerican.com/article/farm-raised-fish-...

- https://www.theguardian.com/environment/2017/apr/01/is-farmi...

- https://www.peta.org/issues/animals-used-for-food/factory-fa...

- http://content.time.com/time/health/article/0,8599,1663604,0...

- https://www.theguardian.com/environment/2012/sep/10/scottish...