after being in this hobby for 5 years now, I believe that Tangs should not
be put in a reef system (unless you're extremely diligent and ultra-skilled at this hobby).
The longer I own a reef tank the more I believe reef tanks should only house a maximum of 4 small fish -and- nothing larger than the size of your thumb. The more populated your reef becomes with coral the more you have to cut back on the number and SIZE of fish.
I have completely retired from owning Tangs in my coral-packed reef tank after killing off about a half dozen over the course of 3 years...and still to this day feel completely aweful for doing so.
Its not fair to a Tang to put them a tank system that cant be treated with medicine. Tangs are extremely sensitive....and big eaters/grazers and easily polute a tank with their big appetites. If a poluted tank is ignored for as little as just one week, a Tang quickly becomes stressed then ill and before you know it you wake up one day with whitespots all over your Tang....and a week later, its laying flat on the sandbed, dead.
I'm sure there are a ton of people on this board who successful keep Tangs in a reef.... but I'm here to tell ya'.... they're consistantly working their tails off to maintain an unpoluted tank....and put PRISTINE
water quality at the TOP of their list.
So in my book, if you want a Tang in a reef, you need to be a very DILIGENT hobbyist by 1) stepping-up water-changes to once a week, 2) monitor your water quality daily and be prepared to do a water change at any given moment, 3) be a mastered-pro at feeding, by providing garlic-soaked food and in small amounts...just enough to keep them happy but not so much that your water quality go bad...its a delicate balance must be maintained 24/7 365 days a year
....its all just too much work and too hard for 90% of hobbyists.
If you aren't ready for such a diligent commitment, leave the beautiful Tangs at the LFS where they treat their tanks with medicine constantly and use a much lower salinity
to keep them healthy and ready for sale.