Ok if you want to get picky, SG
Another thing to consider, like with any ailment, IE: viruses, bacteria or protozoa. there are different levels of infestation and there are different organisms in each family that may or may not respond well to various treatments. If hypo dosn't work in a particular case, why mess around and lose fish when there are faster and proven ways to eradicate? Sure the conservative approach is nice, but it doesn't always work.
Yes I know that Tangs are sensitive to copper treatment, but Cupramine is well tolerated and you can also go for a lesser time period.
, I did the hypo treatment by the book, and it simply didn't work in this case. I'm not the only one that has reported this.