I think Butterflyfish are
pelagic spawners
that is, they release many buoyant eggs into the water which then become part of the
plankton, floating with the currents until hatching. The fry go through what is known as a
tholichthys stage, wherein the body of the post
larval 
fish is covered in large bony plates extending from the head. They lose their bony plates as they mature.
[3] Such a curious armoured stage is seen in only one other family of fish, the scats (
Scatophagidae
_________________________________________________________
Tummy Tuck
Brustverkleinerung