The problem with Ich is that it will continue to live as long as it has a host organism. Treating in a quarantine tank is why this is important. If you have more than one fish in the tank, and you remove the infected fish, if the Ich has dropped spores they fall into the substrate and will infect the other fish in the tank, and the cycle repeats. Also Marine Ich is different from FW
Ich from what I understand.
I've heard that freshwater dips will work, you get in infected fish out of the tank, put it in a temperature-matched freshwater (RODI
) bath for about 5 minutes, and this is enough time to kill the parasites but not the fish. If you're lucky enough that the Ich hasn't reproduced yet, this may take care of the issue.
However, if it doesn't, you will likely have to remove all the fish to a QT and treat them in that tank for 30 days. I think Marine Ich has a 28 day life cycle so if there's no host in the DT then they will naturally die off from starvation essentially. However, that 28 day period is from the point they drop off the host and start the new life cycle, so you may want to wait longer. Also I think if you lower the salinity in the DT (hyposalinity) the Ich will not survive. However, there is a fine line between low enough to kill Ich and too low that will kill other wanted organisms.
Perhaps someone with some experience treating Marine Ich can chime in. I haven't dealt with it before. I do know however that you have to treat it rather quickly.