Does a freshwater dip get rid of ich? Do you have a quarantine tank?
I read on
http://reefkeeping.com/issues/2009-04/newbie/index.php
that a salinity of 1.009 was needed for combating ich. Definatly shouldn't do this in your display tank though. After about 48hrs of 1.009 slowly raise it back up to normal salinity and just watch them for signs of ick for about a month.