Acanthurus japonicus( powder brown tang) is sometimes delicate and hard to keep according tho Scott Michael"s "Marine Fishes" I would not keep another Acanthurid with it . In a 75 . I agree with Gary ; in a 75 g one tang is a safer course. If you're absolutely set on another tang , avoid acanthurus and zebrasomma species. Perhaps a Ctenochetus ( tomini or Kole) could work but it's risky in a 75 gallon.