This is actually the Valentini Puffer, the Blacksaddle Filefish has a much longer dorsal fin that comes further up the head, as well as a dorsal spine that is lacking on this fish.
See this excellent picture of the filefish for example: Blacksaddle (Mimic) Filefish - ZooChat
@Great Argus : Thank you for the correction ! I've made this misstake already before but forgot about it yesterday-night when I uploaded this photo ( must be because it was already quite late ).
