The problem is that carnivore fishes are tasty, and vegetarian fishes... not so much. You can't just replace all their food by plant stuff and expect a good gro

The problem is that carnivore fishes are tasty, and vegetarian fishes... not so much. You can't just replace all their food by plant stuff and expect a good growth. 5-10% of soy, maybe, I' don't remember the exact value, but > 50%... No way. Fishes get ill and growth is stunted. It promotes cannibalism also. Premium fish food for aquaculture is expensive.