It really depends on how you have aquired the animal. If shipped via an etailer, the amount of ammonia in the transport bag will be higher depending on travel time. The good thing is most use pure O2
to fill the bags. With local pick up, this is not usually a concern.
The biggest mistake made by hobbyests in either case is not allowing a proper temp acclimation before
opening the transport bag. This is a very important step. The increased/stabalized temp allows for the pH to come up some which helps prevent shocking the animal. This moreso is the reason for sudden losses along with too quick a change in salinity. The increased pH will increase the toxicity of ammonia but is very easy to dealt with if you keep a good detoxifier on hand. Everything I buy no matter the time transported gets a few drops of Prime
added to the bag after a proper temp acclimation. This will detoxify (not remove) harmful ammonia and bind copper if used.
You can then test the transport waters salinity and manipulate the QT
salinity to match before you begin acclimation. It's a quick process and does not add much time at all. Then it's simpley matter of chemistry acclimation. More often than not an LFS
will keep a lowered salinity which helps in the stress of fish and also has a side benefit of saving on salt. Fish cannot quickly adapt to increases in salinity and must be done over days, not hours. If added to a QT
with a matching salinity, the level can be raised nearer the time when it will be transitioned to the main over a period of days and not further stress the animal.
More often these two (pH/salinity) are the cause for "why'd my fish die"