Thats what people in the hobby call a Hippo or Regal tang. I hate it when they call it the Dorie fish!!!!
Most people I know do not agree with that 70 gal
requirement. That fish can get 12" when full grown and it will have problems in a 75.
My Marine fishes book says min 100 gal
... Tangs like to swim so they will require IMO
a larger tank.
It is your tank so do what makes you happy... There are a lot of 2" hippo tangs around lately..