I had absolutely no idea, but I hate to see a thread without a reply.... so I did some googling for ya. Hope this helps and GL! :



http://www.aquahobby.com/marine/e_chelmon.php
.........Sexing: Males may have a steeper head profile



http://animal-world.com/encyclo/mari...terflyfish.php

Sex: Sexual differences: No sexual difference is noted for this species. Butterflyfish species studied up to this time indicate that these fish are gonochoristic, meaning that each fish is either a male or a female and they do not change sex.




http://boardroomaquatics.com/Copperb...erflyfish.html

Sexing: Difficult / Impossible