The best method for soaking bacalao is to cover the fish with approximately 2 inches of cold water in a large bowl. Put the bowl in the refrigerator and soak for up to 3 days, changing the water at least 3 times a day.
Different brands and varieties of salt fish differ in degrees of saltiness. Less salty varieties need less soaking time, sometimes just one day. You can test it by tasting a small piece for saltiness after 24 hours of soaking. You want the bacalao to be slightly salty, not overpowering.