Sexing frontosa is typically difficult at best,
even for the experts. I have seen exporters, importers, breeders and
aquarists sex frontosa incorrectly. It's not that it can't be done, but it
can be difficult.
There are several indicators
that point to the sex of a frontosa. None of these points can be used
until the fish are at least three inches, in my opinion.
1) Behavior- If one has ample time
to observe a group of frontosa in a aquarium, there is a chance to sex the
fish just on observation. This is especially true if the group had grown
up together or at least has spent enough time in a particular aquarium to
When a group of
frontosa is grown up together in a group of six or more, it is almost
guaranteed that the largest specimen is a male. Males generally grow
larger then females and grow more quickly. A male must fight aggressively
to become "king" of the harem. A larger fish has a better chance of being
dominant thus the largest fish in a group is a male. If that male is
removed from the group, a subdominant male will have a growth spurt and
take his place.
Quite often a new hobbyist
will believe that out of his group of frontosa, the largest is a male and
the rest are females. While this may be the case, most likely it is not.
Subdominant males may remain small because they have to in order to avoid
the dominant male's wrath in the
Males will also show aggression
towards males and try to court females. You must watch carefully and
patiently for a male frontosa to show his courting dance. It consists of
the male listing to one side slightly while folding his fins. This may be
followed by a slow sweeping circular motion over the substrate of the
aquarium. It is a gentle gesture and is much harder to spot then many of
the rift lake cichlids.
Often, sellers of
frontosa groups have a more then optimistic idea of how many frontosas in
a group are female. Buyer beware!
2) The nuchal hump-
The hump on the head of the frontosa is actually an extension of the
dorsal muscle. While there is no doubt that large older dominant males can
have enormous humps, it is by no means a definite indicator of sex. I have
seen females with large humps many would swear are males. I have also seen
males that have a hardly any hump at all, many times there were
subdominant males. All adult frontosas have a hump to some
3) Venting or tubing- "Venting" or Tubing" actually involves viewing the sex organs of a
fish in order to determine sex. This procedure is the most reliable method
to sex frontosa, with practice. Larger specimens are easier to sex then
smaller specimens. I personally have a hard time sexing a frontosa by
venting, if under four inches. Frontosa that have already spawned are also
easier to vent as it seems that when a female passes eggs her tube becomes
In the photos below we can see
pictures of confirmed male and female frontosa. There are two holes on
each fish. The one towards the top is the anus. The one towards the
bottom, closet to the anal fin, is the sex organ. You will notice that the
female sex organ is more rounded and the male is more triangular. Trust
me, it gets easier with practice.
individuals may be harder to sex then others. The male pictured below is a
decent example but, I have seen others that were much easier to sex. The
sex organ of the some other males I have vented were narrower and more
triangular in shape. □