As far as how they look I think angelfish and surgeon fish/ tangs would be the closest comparison. All three groups of fish are laterally compressed and seem pretty intelligent. The issue comes from their behavior. The saltwater fish can be territorial, and careful planning would be important to avoid aggression issues. Also, some of the angelfish like to eat coral and other inverts.
As far as how they look I think angelfish and surgeon fish/ tangs would be the closest comparison. All three groups of fish are laterally compressed and seem pretty intelligent. The issue comes from their behavior. The saltwater fish can be territorial, and careful planning would be important to avoid aggression issues. Also, some of the angelfish like to eat coral and other inverts.