The three angels was placed in my tank as juveniles. Sex change occurred quickly and the largest become visible male as early as 2-3 weeks. However, I was visiting a friend of mine who have had a Flameback in his tank for a long time, 2.5 years. This fish was at least 1.5 time the size of my largest fish.
Looking at that fish I can tell right away that is is still a female, due to the slight yellow/orange edge of the anal fin, and very thin border of blue at the back of the dorsal fin, and due to the round shape of the end of the anal fin.
My initial observation is that apparently Flameback angel do not change to male unless it is stimulate to change sex by other, smaller angels.
BTW, according to fishbase, bidirectional sex change observed with Centropyge acanthops. I am sure, like other dwarf angels, there is a lot of sparing and fighting happened before the looser change sex to female.
I have questions for all reefers who keep Flameback Angels:
How long have you have your Flameback angel(s) in your tank?
How many Flameback angel do you have in your tank?
What is the sex of your Flameback angel(s)?
As far as you can determine, what was the sex of your Flameback angel(s) when you first put him/her into our tank?
What was the estimated size of the angel(s) when you first put him/her into your tank?
What is the size of this angel(s) now?