These types of threads sometimes get amuseing with the different sugestions that often pop up without a perfect discription or a good photo.
So, heres another one ...
Very possible that its a hybrid....but between what two fish ? that is known to happen.
This first photo is a hybrid of the Goldrim, sometimes called a Powder Brown, Whitecheek (
A. nigricans ) and the Achilles, sometimes called an Achilles, haha. The markings on this hybrid do vary slightly, mostly in the tail colors...This hybrid is mainly found in Hawaii.
The last two photos are of the pure breeds...
This hybrid is rarely found in the trade but when is, goes for $ 200 or so...
Jonny, Im not saying this is the fish in your LFS, you seem informed about tangs so your call. Hopefully other members may enjoy the info.
You may know that both of these species are very difficult to keep in an aquarium and if you try it, all I can say is GOOD LUCK....