how can you tell male/female?
An experienced reefer told me they have different snout markings and slightly different body shape. Males should have a longer yellow triangle on their nose.
I don't know if this is true but I have paid attention to it and pairs always have different yellow marking on the nose, as in, one has a longer yellow triangle and the other doesnt.
I searched some pics on the net and here you can see the upper one having a longer yellow marking
Offcourse this is not a proven feature and could be a complete coincidence