pajama cardnial help

[UN-Sizzlers]

I have a mature pair and was wondering if there is any visable difference between male and female? they met up at dusk but all day stay apart.

 

[Peter Schmiedel]

Typical all cardinal fish do not show any sexual dimorphism. Unless you find the male with eggs in his mouth and are able to distinguish the fish by color patterns there is no way for the hobbiest,