I will tell you that this fish in general is not easy to keep and you must pay very close attention to every detail when you select one and in how your tank is setup.
I had one for about a year, switching him between my two reefs until he eventually got too big for my tanks. I traded him off to a friend who had been looking for one and had a much larger tank.
They get very large and grow very fast. Most tangs get the majority of their growth in the first 2-3 years of their lives. This is why I think putting off getting a large tank for them is bad because, even if it has been a year or so the fish will already be significantly stunted and will not reach it's natural size.
meeting their nutritional needs can be hard to do. I would suggest that you feed them several small meals a day. They can be finicky when you first get them and I would give them lots of variety.
Another thing is that they need immaculate water and lots of current. They are very fast swimmers so I think they need even larger systems than tangs of comparable size.
Also, selection is key. I can't stress selection enough. They have an extremely narrow margin for stress and do not ship well. Any sign of physical damage, trauma and I would reject them on the spot. Also Check to see how they are eating. If they are ignoring food than chances are they will not eat for you. avoid any that are skinny as they have an even lower chance of recuperating. They should be cruising around the tank very quickly and they should be very alert to your coming near the tank.
I bought mine at about 3 inches and right when I added him he put
my 5-6 inch sailfin right in its place. They may be kind of shy when they are smaller, but when they get big they can be very agressive.
If you get one they are totally worth it if you are willing to care for them because they are definately a beauty.