https://www.saltwaterfish.com/site_11_03/acclimation.php
they say about two hours. i usually dont dip this long, but you have to if you want to get the live guarentee from SWF. i always check the salinity of the bag water before i start dripping because most fish stores will keep their salinity much lower than mine to try and stave off parasites. if the difference is really great then a longer drip is needed. if the water qualities are similar i only drip for 30-45 min.