In order to successfully vent fish, you need a "clear" photo of the under belly of the fish, where both the anus and sexual vent are visible.
A side view can be very misleading, and almost impossible to ID from, unless they are actually spawning.
Holding the fish and viewing the under side, in females, both vent and anus will be similar a size.
In males the sexual vent will be smaller than the anus.
The female below is easy to distinguish, because she is in the act of spawning.
Once spawning is done, or before spawning, from the side, the egg vent is no where to be seen.