I agree there's big differences but the aquarium doesn't have near the same number of pathogens floating around why put the fish through qt when its going into an environment with less pathogens? Wouldn't it make more sense to lower stress levels and put it in as natural an environment as possible? If fish in captivity do not acquire immunity as well then how does anyone who uses NSW keep an aquarium?I wouldnt say the fish has changed at all, its the enviroment we keep it in. we mimic the ocean but I dont believe it will be the exact same, as its only (in my case) a 75g box of water.