+1 to Mebbid with the addition that you can get replacement trace elements supplements for SW
to add back to the water for the fish while in FW
, none or not many exist to my knowledge.
As for the LFS
which didn't change water for 3 years, I am assuming that was in a display tank? If it were in their system, they must be adding water to it replace the water they take out when they sell a fish so they are doing some water changing. If it's their display tank, I can tell you from experience that it does, long term, screw up the fish by not changing water. Unfortunately, way back when
, I too didn't get into the habit of water changes in my marine tanks and no fish I ever traded in survived. ( It was the 70s, we didn't know better yet
) I was always taking small fish and raising them to a larger size before trading them in for small fish again so I would have these fish for months and sometimes years with no problems so I couldn't understand why they would be dying in the new water. I did some research into it and found that the fish would acclimate to the bad conditions but have a really bad time adjusting back to the good water. I can't recall the exact terminology for this but it's the same as when you take a fish from a higher salt level and reduce the salt level too quickly ( sometimes even multiple days is too quickly
), the fish dies from the "shock" of the change. Once I started doing my routine water changes, the trade ins did much better. That was the only difference to my fish keeping so there had to be something to it.
As for the article and fish in cycling, you have to remember that ammonia is natural and there are toxic and non toxic versions of it. Again, way back when, ( Now I'm talking the 1960s
) all we did was fish in cycling, without killing fish. I had many fish that became successful breeders even going through this "fish in "cycling so they were not damaged by the process. You can't automatically condemn someone for doing that style of cycling if it is done under the right conditions.
Hope this helps.