Ok, thank you so much. Last question sorry should I do this process to all the fish in this qt ? Along with black tang i have Oreni and clown fish in this system.1.012 is fine for Neobenedenia. 1.009 is needed for marine ich, Cryptocaryon, but it is riskier to do. I can't advise you on this - the tang didn't show any distinct signs of ich, but its skin was so congested it would be impossible to tell. I'd hate to have you cure the Neo but then lose the fish to ich. On the other hand, going to 1.009 can kill the fish, but if you don't get to that point exactly, it won't take care of ich.
Here is a post I made on hyposalinity:
Hyposalinity
Hyposalinity Jay Hemdal 2021 This term refers to a long-term bath treatment for marine fishes in which the salt content of the water is lowered and held below the point that certain parasites can survive. The salt level reached, and the time of the treatment are the two variables...www.reef2reef.com
Jay
Does this disease stay in water colum and attack other fish ?