The surest feature for sex differentiation is a wine-red spot in the middle of the belly of the female. The spot is very clear and deep red.
However, the stain can only be recognized from a certain size.
At a certain age, males of the same age are larger than females.
The second ray of the dorsal fin is longer than the other rays in males.
In females, the second ray was originally not or significantly less extended. In current breeds, the beam is both at
Mikrogeophagus ramirezi “Blue” male Source: Image on Wikimedia Commons License: CC Attr. SA 3.0 Author: Loup1128
Both males and females are usually significantly longer.
However, males spread the first three rays more apart than females. The rays are placed slightly forward from the male.
Shortly before the eggs are laid, the ovipositor can be clearly seen in the female.
The males are clearly more dominant than the females in the dealer tank.
If you observe the animals in the dealer tank for a while, you can clearly see the differences. Depending on the size of the pool, one or two couples often dominate the pool.
Often they are busy with spawning preparations. The other animals stand more at the edges and in the corners of the pool. There, too, the males are clearly more dominant than the females.
South American butterfly cichlid females and males: