If you mean by a bath ( a dip in saline water). A quick dip won't make a dent, because there re Ick cysts all over your tank, in the gravel, in filters etc etc/. You will need to treat the tank for a few weeks, to get the dormant cysts. When dormant, and on the fish, they are immune to treatment, it is only when they hatch out are their cell walls are vulnerable to the treatment. This can take weeks depending on temp and how fast they hatch out.