I recommend this method for fish from LFS:
Put new fish in container and fill it with 3/4 shipping water and 1/4 tank water. Let stand 5 minutes. Dispose of half the water and fill with tank water. Let stand 5 minutes. Repeat once more. Check parameters. If everything is close (SG off by max .002 measured by refractometer, temp off by max 2 degrees, pH off by max .2), fish can be netted and put into tank, otherwise repeat till the params are close enough. Hydrometers are inprecise so make sure they match up if you are using that to check salinity. No need to put a pump for oxygen. You disturbing the water every 5 mins will deliver enough air.
Fish that are shipped need drip acclimation because shipping water is kept at lower pH (near neutral) to keep oxygen in bag. Pumping or aerating the water would raise pH too quickly and they would die of pH shock.