A fish I have in my marine tank is effected with both ich and another secondary parasitic infection. I wondered what the sucess rate of a saltwater bath was, and how to properly administer one?
The only proven way to cure Marine Ich is Hyposalinity.
You need to drop your tanks salinity down to aprox. 1.010 and leave it there for 4 - 6 weeks. Be EXTREMELY careful though...and monitor the salinity daily. Letting it drop to even 1.009 or 1.008 will kill your fish.
If you have a quarentine tank, that's even better. Separate the infected fish, in your q-tank and do the hyposalinity there.
It's not as if you can just lower the SG in a display tank full of live rock, sand, and inverts- the fish need to be moved to a hospital tank for treatment.
Sure it's a PIA but that's exactly what happens when you don't quarantine them.
Quarantining them to begin with is 1000 times easier.
The display tank will have to remain fishless for a minimum of a month for the ich life cycle to run it's course and disappear.
And 1.009 or even 1.008 will not kill fish. Bacteria, inverts, and everything else, but not the fish.