ID Black dots on yellow tang?

[Delphinus]

4 minutes ought to do it.

It's a flatworm so one treatment is usually enough to get them to literally fall off. In really bad cases maybe two treatments a day or two apart.

FWIW, and maybe this is bad of me, I don't know, but when I was advised what to do, I was told "don't bother matching pH, just use tap water, but DO match the temperature") and the tang was fine and I never had to do it again. (Which is probably good because I can usually catch a fish once, and ever after that they're onto me and I can't get near them with a net.) I'm not sure what you'd have to use if you wanted to match pH. If you could match pH I'm sure it would be easier on the fish.