NOTE: This procedure can not be performed in an environment containing live rock, live sand or inverts [including crabs, corals, etc.] If you have a strictly Fish-Only setup, then the treatment can be done within the display, otherwise, you will need to treat infected fish in a quarantine/hospital tank.
Hyposalinity is a procedure involving lowering the salinity from normal tank levels to 14 ppt (1.009 Specific Gravity) over the course of 48 hours. This is done by doing a series of small water changes using fresh dechlorinated water. During the procedure, pH must be closely monitored as pH tends to drop as water become less saline. Fish are maintained in hyposaline conditions for three weeks after all symptoms are gone. Again, accurate measuring is essential, and the standard swing arm hydrometers are not going to work. A refractometer or large glass lab grade hydrometer calibrated to tank temperatures is needed. Once the fish have been asymptotic for three weeks, the salinity is then raised back to display tank levels over the course of a week. Fish can not tolerate rapid increases in salinity. Leave the fish in quarantine at display tank levels for another week.
Your display will now have been fishless for at least four weeks, sufficient time to allow the parasite’s life cycle to be interrupted. ****** is an obligate parasite that requires a fish host. No fish=No host=No parasite. Ich is a fish-only parasite, it will not affect inverts.
Continue to monitor pH daily during the process and be prepared with buffers to address any pH problems. Also keep the water clean through proper filtration.