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Issue: January 2014

Experiences with Nanochromis transvestitus (Full Article)

Author: José María Cid Ruiz


Photographer: José María Cid Ruiz
A rare cichlid from fast-moving waters in the Democratic Republic of the Congo, Nanochromis transvestitus is a bit of a challenge to keep and breed but will reward you with its stunning coloration and fascinating parental care.

When Stewart and Robert collected Nanochromis transvestitus for the first time in 1973 in the chocolate-colored waters of Lake Mai-Ndombe (Democratic Republic of the Congo, formerly Zaire), they did not doubt that their purple-colored specimens were the splendid males of a new species of dwarf cichlid, but this species held a surprise: The specimens in brilliant red-violet livery were the females. First described scientifically in 1984, the species’ name, transvestitus, refers to this anecdote.

In its natural habitat, N. transvestitus is found next to zones of currents, but occupying the banks, where the flow is more moderate. There, at a depth of only 1 meter (3 feet), on a bottom covered with fallen vegetation from the forest surrounding much of the banks of the lake, these excellent diggers feed in the fine sand on the bottom. The bottom here generally lacks rocky relief.
This is not the only species of dwarf cichlid that inhabits this lake. In 2006, specimens from the same lake were identified as the species N. wickleri.
Description
The basic coloring of the body is gray-greenish with seven broken, dark, vertical stripes. This characteristic pattern in the male is barely noticeable in the female. The female has a striking violet abdomen and unpaired fins that are pigmented black with an intense white stripe. Additionally, the male is more slender, and the edge of the caudal fin ends in a point.
The species is of moderate size, though among well-fed examples bred in captivity, one easily finds females that surpass 4½ cm (1¾ inches) and males that reach 6½ cm (2½ inches).
Care and Territoriality
These fish are somewhat delicate, so their care, just like their reproduction, requires some experience and patience.
To design their aquarium, one must recall their natural habitat of abundant vegetation, part of which is on the bottom in the process of decomposition, causing the water to become very acidic (pH 4.0) and very brown with reduced visibility. Interpreting all this ecological information suggests an aquarium in which vegetation and shelter abound, with diffuse lighting and filtration through peat as well as periodic addition of a liquid component based on humic and tannic acids. By doing this, you can obtain water of the appropriate acidity and hardness for these fish. They like vigorous water circulation, provided there are abundant, dark-toned shelters. For the bottom of the aquarium, select a fine and equally dark sand.
Their diet is not problematic, provided that it is varied. They develop very well with a weekly combination of mysis, Artemia, Daphnia, red mosquito larvae, and different purees that combine meats and vegetables to provide sufficient proteins and vitamins.
Despite their small size, what is not moderate is their character, which shows notable intra-species aggression. I do not have field studies describing their conduct in their natural habitat, but the behavior that I have observed in spacious aquariums (450 liters [119 gallons]) invites me to think that the species deploys territorially with a male dominating a zone inside which there are two to three sub-territories of females in a hierarchical structure, without forming stable relationships. In fact, when I have had couples form and spawn in smaller aquaria (100 liters [26½ gallons]), the cohesiveness of the couple has been precarious outside the period of courtship, spawning, and caring for the offspring.
Formation of Breeding Pairs
As mentioned above, members of this species are very aggressive among themselves. Within a small group, we can expect the largest specimen to attack the others, with an ability to inflict severe wounds. If you isolate that dominant specimen, another specimen will take the dominant position, so there is no way to eliminate aggression in the species. In general, the males perform this role, but I have observed that the females are also very aggressive and if the largest one in a group is female, she will attack and force others to flee, males included.
To counteract this aggressive intra-species behavior, I have utilized two different methods to form couples without a loss of specimens. The first consists of putting a trio of young fish, comprised of one male and two females, in a very spacious aquarium (it is worth recalling that in general, fish and aquarists have historically diverged over what qualifies as a spacious aquarium). In volumes of 450 liters (119 gallons) or more, one normally achieves a stable equilibrium where the male tolerates female sub-territories of reduced size on the periphery of his own and doesn’t pursue the females when they return to their sub-territories. In such conditions and when well-fed, it is just a question of time before the specimens mature, the female displays a certain gravity, and one day, where previously there was persecution, there is now courtship and digging together.
I use a second procedure to form couples when I only have access to smaller aquaria of about 100 liters (26½ gallons). In these cases, I select a young male and a young female of similar size (between 3 and 4 cm [about 1½ inches]) and put them in the aquarium separated by a sheet of transparent, perforated methacrylate. This allows them not only visual contact, but also hormonal and chemical communication.
At first, the male behaves very aggressively and the female avoids him. Over time, the male becomes less aggressive and the female becomes less scared of him. Eventually, they will start to display courtship behaviors, so you can let them interact by creating a narrow tunnel large enough for the female to pass.
If they are ready, the female will go over to the male’s side and continue with the courtship behavior and joint digging. After several days of this, you can remove the barrier and offer them free access to the whole aquarium.
Breeding Nanochromis transvestitus
The peculiarities of this species appear again in its reproduction, given that there are two factors that restrict the reproductive viability of N. transvestitus. The first factor is the pH value. Even when working with specimens that were bred in captivity and that probably developed in water with pH values above the 4.0 of their African water of origin, I have not managed to achieve fertile eggs in water above pH 5.7, even with couples of the third generation. It is easy to identify the infertile eggs because their color does not change in the same way from the initial green-yellowish of the eggs after spawning.
There is a second restriction to keep in mind to achieve success in reproduction: water hardness. In their natural habitat, the water is extraordinarily soft, and the egg is designed for these conditions. Success in reproduction requires soft water, with total hardness values between 6° and 9° GH.
Above 20°, I have not been able to get a new generation from fertile eggs. The failure in embryonic development at that level of hardness is probably due to a problem of osmoregulation in the interior of the egg, which will tend to dehydrate itself to balance the anomalous high concentration of salts in its environment.
The optimal conditions for the reproduction of this species seem to be in these ranges: pH 4 to 5, GH 4° to 9 °, and temperature 27° to 28°C (80° to 82°F).
Spawning and Fry Development
Gravid females generally darken their pigmentation, which highlights the intensification of the red-violet tones in the ventral area and the white stripe of her unpaired fins on a similarly intense black base. The female usually approaches, the male curving and vibrating in a position that clearly shows her violet abdomen. The male, if interested, also intensifies his color, which turns darker, making his vertical stripes more obvious.
Both perform intense, joint digging activities in various places in the aquarium where they have shelter. The female vibrates, approaches the male, and then initiates swimming in the direction of one of these sheltered places, followed by the male. In general, the female takes the initiative, but it is not unusual to see the male repeat the pattern in the hope that the female will follow him. This activity can occur over a variable number of days, in general from two to five. Partial changes of water to a slightly lower temperature than that in the aquarium can trigger this process.
In the end, the couple selects a shelter to spawn in—a hollow in a rock, a hidden wall, a ceramic jar, etc. The spawning usually occurs in hours of weak light; it is not easy to observe without disturbance, and it lasts a fair while, between 40 and 60 minutes on average. The number of eggs laid in my case, after three generations, has oscillated between 30 and 70, depending on the size and age of the female. The size of the eggs, which are of elliptical shape and a yellow-greenish tone, varies between 1½ and 2 mm.
As soon as they have spawned, the roles of male and female are clearly set: The female will care for the laying—still displaying an intense coloration—while the male guards the periphery of the territory. The male visits the female and the laying as much as possible. The behavior between them is reminiscent of that during courtship. If the couple does not suffer external stress, they feed relatively normally in this period.
You will not see the couple swimming with the shoal of larvae around them until nine days after spawning, but some prominent things will happen in the meantime. For example, embryonic development is completed at a temperature between 27° and 28°C (80° and 82°F) in the first five days, after which the larvae emerge. In 90 percent of cases, after the birth of the larvae, they are transported by their parents, especially by the female, to a second shelter where, over four more days, they complete their development while reabsorbing the yolk sac that feeds them. The larvae at birth measure 3½ mm (and four days later, upon beginning to swim, they already measure 6 mm). The larvae are clear to cream-colored and have a dark, speckled pigmentation like the skin of a leopard.
During the period from the spawning to the fry swimming freely, there is invariably a large reduction in the number of larvae compared to the number of eggs, and subsequently another reduction in the number of fry that begin to swim relative to the number of larvae born. After observing many similar processes with the same result, the truth is that I have not managed to explain with clarity this process of numerical reduction.
The shoal is led around the aquarium alternately by the male and the female, but mostly by the latter. Sometimes both parents simultaneously take the fry around the aquarium in search of food. Vigilance is very strict, and at the least sign of danger, the female vibrates her body, which leads to the immediate immobilization of the shoal around her, then slowly the female takes them toward a secure shelter until the potential danger disappears.
During the night, they are similarly transferred and concentrated in a rock cavity or in a depression dug into the bottom where the parents watch closely.
Once they begin to swim on the ninth day, they begin to feed on brine shrimp nauplii two or three times a day. The diet of the fry is not problematic because they are always voracious and not selective. In addition to live and frozen nauplii, they accept frozen and freeze-dried Cyclops.
The fry grow very fast. At two weeks, they already measure 1 cm (¼ inch) and display an initial dark stripe. When they reach one month old, I usually separate them from their parents and transfer them to a development aquarium. The operation is slow, since they are very fast and difficult to trap. By then, they surpass 1.3 cm (½ inch) on average and they already display the vertical dark stripes of adults. In the new aquarium, weekly 50-percent water changes are essential for correct development. The diet is then supplemented with dry food in the form of finely crushed scales. The mortality rate in this phase is practically nil.
At two months old, with an average size of 2 cm (¾ inches), they are already very territorial and have constant skirmishes for the control of any small shelter. They have greater activity during the hours of dim light (dawn and dusk), remaining in their shelters during the hours of artificial light, abandoning them only to eat or during territorial skirmishes. The diet at this stage of their development is similar to that of adults.
Second and Third Generations
In the following generations, I have observed that normally the specimens’ sex is first apparent at about 4½ months. At that age, at sizes of about 3 cm (1¼ inches), the female specimens already display white stripes on the caudal fin and the males have the dark vertical striping and the termination in a point of the dorsal fin. I usually separate the better specimens in couples or trios in particularly spacious aquaria to promote their development and pairing. In these conditions, at six months of age, one frequently observes the first signs of courtship behavior in the more developed females.
I have recorded the first stable pairings at eight months and sizes of 4½ cm (1¾ inches). First spawning can happen from month 10 to month 12.
I have followed the reproduction of the species to the third generation in my aquaria without observing any degenerative symptom in the specimens; they have reproduced normally. The proportion of males to females, in contrast to what I would have expected, has been slightly higher for the males.
The monitored longevity of the specimens has reached three years, but I cannot say whether that might be the limit for the species.
For more information or to contact the author, visit www.aquaticnotes.com.

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