IMO it is the right combination of both nature and nurture that grows big fish. Genetics, diet, time, and water temps all play a role.
Artificial feed can grow big fish, but it might might not let them live long enough to grow to record a size.
And since we don't have species specific feed, the one size fits all approach may not be the best for their health. I.e., lots of fatty deposits and fatty livers due to too many carbs in the diet.
