Sexing Serpae Tetras

[korunks]

I have 5 longfinned serpae tetras and am interested in breeding but am having significant trouble sexing them. So how does one sex a serpae tetra?

 

[helterskelter]

Females get larger and the female will have a slightly larger belly to her.

I'm not 100% but i think the males have a slightly larger and better coloured dorsal fin.