There are some cases where certain species demonstrate pigment differences
between the male and female vent. And with some species, males will have
an elongated and tapered genital papilla, such as the Julidochromis regani.
With these males you can move your finger across the vent region from
left to right and the genital papilla will also move.
When venting your fish, be sure to handle the fish only with wet hands.
I have found that grabbing them with a net gives me a little extra grip
so that they can't slip out of my hands. Also be sure that you do not
keep them out of water for more than about 30 seconds. You want to make
this as un-stressful as possible, so try to keep the number of times you
examine them down to no more than 3. Once you have sexed your cichlid,
you will want to keep it separate from other un-sexed cichlids. Think
about how you are going to address this before you start handling them.
There are other methods aquarists use to sex their cichlids, albeit
less reliable. Some of these include noting behavioral differences, size
differences, body and fin shape differences, as well as the presence of
egg spots. Most male Mouthbrooders have at least one egg spot on their
anal fin, if not many more than this. Unfortunately, there are only a
handful of species where males exclusively have egg spots. Many females
also commonly display at least one egg spot. This fact makes relying upon
the presence or absence of egg spots unreliable at best, but it can still
be helpful, as males tend to have more egg spots than females of the same
species. Note this is a broad generalization.
Another "shotgun" method is relying upon body size, as males
are often larger than females. And then with some species, particularly
Lake Malawi species, fin shape is a somewhat reliable method for determining
gender. Below I have posted pictures of wild pair of Auloncara
hansbaenschi. A difference
can be seen by looking at the most posterior portion of their dorsal fins.
Males' dorsal fins end with an exaggerated point, while females' dorsal
fins end with a rounded curve.