I read through the suggested internet website from the main thread and quickly ascertained that it leaps around a few questions in elementary logic that have never been met by fish farming proponents.
First:
There is something many ecologists believe is paramount in the management of our environment called the precautionary principle, which states that in the absence of scientific consensus that something is harmful, the burden of proof that it is not harmful falls on those taking the action. In a medical context is the principle of Primum non nocere, or "First, do no harm".
So:
It has been demonstrated time and time again that fish farms have negative impacts on the environment around them and to wild fish populations as they are point sources for high densities of viral particles and parasites. They entangle pinnipeds which are sometimes killed, produce poor quality fish when compared to wild alternatives, are a horrible waste of marine biomass due to conversion inefficiency from fish feed, have invasive potential from escapes, among many other problems up and down marine food webs. From personal observation, they smell horrible, operate in otherwise ideal passageways for wild juvenile salmon, create intense parasite loads on surrounding wild juveniles, are prone to dangerous viral outbreaks that may at any moment decide to cause disease to wild fish, among many other negatives.
Then:
If the above block of text causes you any hint of doubt that they may be bad - then refer back to the precautionary principle and the review the material provided in the link on the first page of this thread and ask yourself if you are convinced they exist in a vacuum, and have zero impact on anything.
Jon