What you describe works great for many fish, even tangs. Absolutely not for this one, and many other acanthurus tangs. I agree though for several fish this may work and did for me for almost a decade, although I had no fish for more than 5 years that's a half hearted success I was content at the time.
These days velvet is far more prevalent than it has been which changes things significantly. Ich is peanuts to velvet.
Don't want to be a Debbie downer but I do want other readers to know and understand that this is a species of fish that is vastly different from many others, and encourage them to read the acanthurus tang and ich management thread I posted above.
Your thread is titled "Achilles 101" which implies education and the forum browser doing their research (probably nowhere near 9 months worth) would probably come here expecting such to some degree so I want to make absolutely sure everyone knows that this is not a recommended way to treat this fish and the risks (to this fish and the others in the tank and potentially future fish additions) and aggravation inherent with your choice.
Spoken from what I would call the most thick skulled, stubborn, break the rules, learn everything the hard way hobbyist I was for over ten years I have a lot of experience with what I say on these fish.
And while on the topic I currently own two Achilles tangs, one powder blue, and a powder brown. I have about 15 tangs, 7 or 8 of them are acanthurus tangs. They pbt and PB fall in to the same category and requirements except that Achilles are about twice as susceptible as the rest, but the story is the same for them as well.