I have been wondering something, and searched a lot, but I don't see that anybody has asked this question before.
Why is it at the pet shop the put fish from different tanks in the same water from 1 tank, but when you come home everybody say you have to float the bag, slowly adding aquarium water to acclimatize the fish, when they don't do this at the pet shop.
Setting up my aquarium nearly half a year ago, I bought to begin with mollies, guppies, angels and the LFS put water from one tank in the bag, and then fish from different tanks in that water. Today all they fish are still alive, so we do know it didn't kill them.
And then again around a month ago I added 4 marbled angels from another LFS, and strangely I watched carefully so I am sure, the man put water from the Goldfish tank which is cold water, and then took the angels from the tank and put in that water which he then put in the bag with the fish.
Today all 4 angels are still alive, so can fish just be moved without the acclimatizing? I was a bit worried when I saw what the man did, but living in Turkey and hardly speaking the language, I couldn't tell him I would rather want the water from the tank the angels came from. But survived did the fish, and they are still alive.
Is this acclimatize process just a myth?
first off that is horrible practice by the LFS. especially taking goldfish water for tropicals. all of there tanks likely have the same ph gh and kh so it will not shock the fish.
when bringing the fish to your home aquarium it is a little different story. first and foremost you have to get the temp in there bag up (reason for floating the bag).
when you are adding your tank water to the bag you are slowing bringing them to your tanks ph gh and kh.
and last always be sure to net the fish out of the bag and not dump the LFS water into your aquarium.
In a shop like petsmart, all the fish share the same water. They are on the same heating system and on the same filtration so if one tank has a sick fish, all fish have been exposed. That saw method means that the water conditions are the same throughout all the tanks. Acclimation needs to happen at home because your tank has different conditions from the shop.