Well, its good to float them to get the temp equal, but to ease the transition to the different water in your tank, its good to take a cup of water from the tank and add it to the bag. Every five minutes or so, another cup.
Even better would be to float, then setup a bucket with a drip line made from airline tubing with a knot tied in it to regulate the flow, use that as a siphon from the tank into the bucket of the fish and fish store water, let it drip in for maybe half an hour or an hour even, then net the fish out and put it in the tank. You will notice the fish is more active as its not like he was taken from one atmosphere and tossed into another. No rule to the methods, other than the slower the acclimation the better. And there is a couple of things we acclimate for, not only the temp, but the water as well.
Cheers

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