There are ways you can visually sex them but it does take practice and is not practical unless the fish is fully grown. That being said here is a good post from a member on another forum.
"Even with all these traits that lean toward one sex or the other, the only way to be 100% sure is to see it breed. When the breeding tubes are out it is usually a piece of cake. Female tubes are very thick and take on more of a squared off shape. Males are very small and come to a point more like a triangular shape.
What characteristics to look for
Here is a list of the characteristics I look for to help determine the angel's sex:
General body shape - Female: round; Male: angular
Head shape - Female: flat, ski slope shaped; Male: forms a hump
Eye/Nose band - Female: flat, inline with forehead shape; Male: develops a ridge at maturity
Dorsals - Female: held slightly backward, in line with the forehead angle; Male: fully erect, forms almost a 90 degree angel with the head bump
Ventrals - Female: tends to hold ventrals closer to the body; Male: held erect, forming a distinct angle with the body
Lateral line - Female: nose tends to be slightly elevated compared to the tail; Male: nose and tail are fairly horizontal
Many of these traits are fairly minor characteristics. But add them all up together and one sex or the other tends to stand out.''
Link to OP
https://www.fishlore.com/aquariumfishforum/threads/the-big-mystery-how-to-sex-angelfish.128849/
