IME most Tangs are very demanding/sensitive fish that need LARGE tanks to prosper, and the love affair might end when they have seemingly nonstop problems in too small a tank. Esp ones that truly need a lot of room, like blues and sailfins. Ive seen very few Blue tangs over the years that didn't develop serious HLLE or die quickly when in a sub-200 tank.
I recently had a whitetail I rescued from a local club members 500g tank leak that developed serious HLLE in a 20g quarantine tank over the course of 2 weeks, and never recovered

Granted, he was full size already...