Chico - I have been dealing with the same LFS for >>20 years, and they do not follow the practice you describe, so do not kid yourself that what is done in one shop is universal practice. The minimum is the practice Dragon Lord Tia describes, but only for the hardiest fish, all more sensitive types get the acclimatization described for discus.
When fish are shipped they are rarely shipped in plain water, and are there for hours (from the distributor to the lFS) to days (from the collector to the importer). That water may well be heavily polluted. But I live 10 minutes from the LFS, there is hardy a pollution issue involved. But I do have different water from the LFS, and the osmotic differences are easily measured and real, just as they would be for SW fish. Therfore I adjust with care. I have never had a fish frantic in a bag - in fact I tend to use catch buckets, not the bag, and add plant cuttings for security, and have the tank lights off or all strips but one off - why should the fish panic? I have never had a fish damaged by my techniques, nor had any subsquent symptoms of ammonia burns to the gills. The nightmare straw men described are largely that, straw men, drawn by taking the extreme cases of multi-day shipping and applying that to brief uncrowded transport from the LFS home. A Halloween story to frighten the unthinking or inexperienced, IMHO & IME.
Your fish, your tanks, handle them as you wish. I will follow a bit more conservative practice for my fish.
When fish are shipped they are rarely shipped in plain water, and are there for hours (from the distributor to the lFS) to days (from the collector to the importer). That water may well be heavily polluted. But I live 10 minutes from the LFS, there is hardy a pollution issue involved. But I do have different water from the LFS, and the osmotic differences are easily measured and real, just as they would be for SW fish. Therfore I adjust with care. I have never had a fish frantic in a bag - in fact I tend to use catch buckets, not the bag, and add plant cuttings for security, and have the tank lights off or all strips but one off - why should the fish panic? I have never had a fish damaged by my techniques, nor had any subsquent symptoms of ammonia burns to the gills. The nightmare straw men described are largely that, straw men, drawn by taking the extreme cases of multi-day shipping and applying that to brief uncrowded transport from the LFS home. A Halloween story to frighten the unthinking or inexperienced, IMHO & IME.
Your fish, your tanks, handle them as you wish. I will follow a bit more conservative practice for my fish.