Well Doch please read this short article and I would invite all to do so as in my opinion it is a reasoned discussion by an author and expert and it happens to be on the exact tang you are considering.
http://reefkeeping.com/issues/2003-03/hcs3/index.htm
Summary
"This works out to 25m2 per sub-group, or just over 3m2 per animal or about 10f2, or about the size of any of the commercially available 125-gallon aquariums. Hence, I would propose this is a good starting point as the absolute minimum aquarium size for any solitary individual"
After carefully reading it would you kindly post your opinion on the article.
If you were considering a ctenochaetus species (bristletooth) consider this article by another author.
http://reefkeeping.com/issues/2003-07/hcs3/index.htm
Summary
"It is unlikely that a four-foot long aquarium will provide a suitable environment to match these natural growth patterns"