I'm glad you're having success with your individual, Dmorty.
The point of the primer is to share both the success and failures of keeping that fish. Having said that, we have to consider the Seagars's aquarium and his experience in the hobby before we can advise him further. To suggest that anyone keep an achilles tang without prior knowledge to the hobbyist's experience is irresponsible.
The fact of the matter is that most achilles tangs that are collected for the hobby die either before reaching the wholesaler or in the first few weeks of being kept in captivity. This doesn't mean that ALL individuals are doomed, but there's enough to suggest that we're killing more individuals than we are keeping them alive. This raises the question of why we are still collecting them and why we would recommend someone keep it.
Below are basic quotes from a couple of webpages stating that the achilles tang is challenging.
"experts only" -
https://www.liveaquaria.com/product/325/?pcatid=325
"Calling the Achilles tang one of the more demanding members of the Acanthurus clan is an understatement. Like many surgeonfish, these guys are highly susceptible to ich and head-and-lateral-line erosion."
Source:
http://www.tfhmagazine.com/saltwater-reef/feature-articles/the-achilles-tang-acanthurus-achilles.htm
"When we look at all the potential problems existing with this species—susceptibility to parasites, feeding difficulties, aggressive or passive nature regarding tankmates—it might seem crazy for anyone to even think about housing one."
Source:
http://www.tfhmagazine.com/saltwater-reef/feature-articles/the-achilles-tang-acanthurus-achilles.htm
"The Achilles Tang is one of THE most challenging fish we have collected, shipped, and cared for. It is sensitive to ammonia poisoning, is an extremely difficult species to handle, and therefore should only be kept by an experienced aquarist.
It sounds silly, but this a fish that seems to break out with ich if you even look at it the wrong way. The Achilles Tang can be a picky eater, and may not readily accept foods offered."
Source:
https://www.thespruce.com/achilles-tang-profile-2925718
"***Prior to purchase, please bear in mind that the Achilles Tang is a very demanding species that requires an aquarium planned around its well-being; the tang should be made the centrepiece of the tank, with all the other variables worked around to suit its specific needs. Experienced aquarists only***"
Source:
https://www.fishkeeper.co.uk/databank/achilles-tang