My usual response:
Ich is an obligate parasite. Usually I suggest ...
1) quarantine all fish for six weeks in quarantine tank. (i.e. plastic container or trash can)
2) Start by bring the
salinity down slowly to 1.020-1.022 in quarantine tank.
3) Purchase a copper treatment, such as Seachem Cupramine ( quarantine tank only ) and follow directions.
4) Make sure the fish are eating well.
5) Bring temp to 86 degrees in empty display tank for 6 weeks.
6) NEVER EVER use copper as a treatment in your display tank.