I have had tangs for over 20 years and have been on many dives with them in the wild.
Different tangs need different things. Hippos are easier than yellows for example IMO
. Hippos cruise around while yellows fly. Tangs need these things to survive and not act as a breeding ground for parasites (they have a very thin slime coat which acts as a fishs immune system);
A long tank for uninterrupted swims, my tank goes around a corner, so the tangs can't see the end. I suggest 6' or more for long term care.
Lots of hidey holes and holes for sleeping.
A almost never ending availability of Nori or other seaweeds to graze on. Seaweed doesn't have much nutrition in it, so they eat a lot of it.
Most of my tangs are almost 10 years old and fat.