Tropheus, Delicate Treasures of Lake Tanganyika
Juan Miguel Artigas Azas
Since their initial importation for the aquarium hobby in the late 1950s, Lake Tanganyika’s Tropheus have enjoyed the attention of aquarists all around the world and are currently some of the most popular aquarium fish. This is the case regardless of the difficulty in keeping them alive in an aquarium, and the even higher level of difficulty in successfully breeding them.
Tropheus are among the most interesting of cichlids, differing from all other mouthbrooders in the family Cichlidae by having a unique reproductive behavior. Their social behaviors and interesting habits, as well as their high variability of color patterns, have been the subject of hundreds of studies.
Tropheus Cichlids in Their Natural Habitat
There are four generally recognized species of Tropheus, to which over 120 color variants have been assigned, including one xanthic form. And in addition to those four recognized species (Tropheus annectens, T. brichardi, T. duboisi, and T. moorii), at least six potentially undescribed species are also recognized and awaiting scientific description (T. sp. “black,” T. sp. “ikola,” T. sp. “maculatus,” T. sp. “mpimbwe,” T. sp. “red,” and T. sp. “viridescens”). In his book Tropheus in Their Natural Habitat (Cichlid Press, 2013), Ad Konings offers diagnoses for all the potentially undescribed species.
These fishes occur on every rocky shore found in Lake Tanganyika, spanning the four countries that share a shoreline with the lake: the Democratic Republic of Congo (four species), Zambia (two species), Tanzania (four species), and Burundi (two species).
Tropheus species inhabit rocky habitats in shallow parts of Lake Tanganyika to a depth of about 30 meters. The rocks vary from baseball-size to huge boulders. Tropheus inhabit mostly the upper layers of the rocky areas, where the rocks are covered with a layer of aufwuchs, algae mats that are mainly composed of green algae, blue-green algae, diatoms, and small organisms.
Tropheus cichlids specialize in feeding on the blue-green algae in these mats, which is easier to digest than the green algae. The shallower areas of the habitat have more light penetration, richer aufwuchs, less sediment covering the rocks, and consequently, more Tropheus.
The outer teeth of Tropheus species are bicuspid, close together, and found very near the outer edges of the jaws. This arrangement helps the Tropheus hold on to individual short strands of blue-green algae that can be cropped by cutting them or pulling them, which they do either by shaking or moving their head while holding them with their teeth. Tropheus prefer to feed in areas where other cichlids, particularly Petrochromis, have combed the algae mat and removed the diatoms on which those fishes feed.
Tropheus prefer browsing clean areas, but such sites are scarce, so they either maintain feeding territories that they defend, or form large foraging schools numbering in the hundreds, which roam through the rocky habitat and visit sites that are heavily defended by other cichlids. They feed off the rocks in their territories under the protection their numbers provide.
Tropheus in the wild grow to about 4¾ inches (12 centimeters) for males, with females a bit smaller, about 4¼ inches (11 cm). They grow throughout their lives, relatively faster during their first two years and attaining adult size during their third year, after which growth slows down significantly. In the wild, Tropheus can live for as long as 10 years, although specimens older than six years are relatively rare.
Populations of Tropheus are much localized and have a strong geographical isolation, normally enforced by impassable sandy or muddy tracts of shore separating the rocky reefs. This accounts for the many geographical color variants encountered in most species, particularly in T. moorii. It has been found that there is hardly any gene flow between populations, and that the color patterns are based on genetic differences and not environmental factors.
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Reproduction & Fry Care
Pair formation always starts with a female migrating into a male’s territory. In T. moorii, it was found that the female is allowed in the male’s territory, grazing on the algae and conditioning for up to three weeks before spawning, but she leaves the male’s territory after spawning and hides among the rocks.
Spawning in Tropheus takes place inside the male’s territory, and is often preceded by a pseudo-spawning phase when no eggs are deposited. Unlike other mouthbrooders, the eggs of one Tropheus female—at least for the species without sexual dichromatism—are fertilized by only one male, which is known as sequentially monogamous.
Tropheus produce a rather low number of eggs, usually ranging from 2 to 15. But while fewer, these eggs are among the largest found in the family Cichlidae, up to 6mm in diameter. The incubation period averages 31 to 33 days, depending on the species, but it is known to continue for up to 10 weeks in the aquarium.
The males do not take part in parental care, usually chasing females away immediately after spawning. In the aquarium, males may tolerate females in the immediate surroundings of their territory.
During the mouthbrooding period, after the eggs have hatched, females forage carefully from the aufwuchs to feed the fry inside their mouths, and in some species also probably themselves, though some females appear very emaciated after four weeks of mouthbrooding. The fully developed young (at least in some species) are periodically released by the mother in sheltered areas to forage.
Tropheus give birth to rather large and well-developed young, which after being finally released look for shelter among the pebbles and rocks in the extremely shallow water. After releasing the fry, females resume their guarding of a feeding territory, and it takes several months for them to recover from the previous breeding effort and be ready to spawn again.
Tropheus can be bred in the home aquarium. For those species that are not sexually dimorphic, venting them is usually the best way to tell sexes apart. Put your Tropheus in a bucket with water, and with a wet hand hold it upside-down with the ventral area towards you. Then, with a magnifying glass, look at the vent; males have a small genital papilla slightly larger than the anal pore (which is closest to the anal fin), while females have a much larger one. Some experience is required to reliably sex them, particularly young individuals.
Once a pair spawns in an aquarium, the female should be gently removed to a nursing tank, which would be a small tank with a sand substrate and some hiding area. Typically the female will release her fry naturally in such an environment. About a week after the fry’s release, females can be returned to the colony, and a larger rearing tank for the young will become necessary.
Aquarium Care
Since the first Tropheus were imported from Lake Tanganyika in the late 1950s, they have enjoyed a great deal of popularity among aquarists, lured by their unusual shape, beautiful colors, and social and active disposition. Nonetheless, in their early days in the hobby, they immediately got the reputation of being impossible to keep alive, let alone breed.
At that time there was little to no information about their habitat and natural history, but when this information started to become available to their keepers, things started to change. Tropheus have not stopped being difficult to keep, and if you add the fact that they are expensive fish, it is important to carefully study them before you intend to keep them.
In researching for this article, I reread Ad Konings’ wonderful book (Tropheus in Their Natural Habitat) that I mentioned above. There is plenty of information about Tropheus out there, but sadly much of it is incorrect. If you read this book, however, you develop a very good understanding for Tropheus, and may even fall in love with them.
The book is based on hundreds of scientific papers, and the vast experience of the author in observing and photographing them in their natural habitat. I myself have also been lucky enough to observe and photograph Tropheus in Lake Tanganyika, and quickly realized that the lake fauna would be much poorer without them.
Tropheus are aggressive and social; you cannot aspire to maintain a pair of them, but need to aim for a group.
As they are expensive, the best approach is to go for a group of juveniles and place them in the aquarium all at once for them to develop pecking orders and territories. The Tropheus aquarium should not be smaller than 5 feet (1.5 meters) in length and 110 gallons (about 400 liters) in volume, with larger being even better.
If you want natural décor, you should consider placing large rocks or a group of them in the tank. It is advisable to arrange them in at least two mounds, as they serve for Tropheus males to establish their territories. Be sure to securely support them, as such heavy rocks may break the aquarium bottom if they slide.
The substrate can be provided with a thin layer of sand or gravel. For a less aesthetic but practical approach, flowerpots or other objects can take the place of rock structures, and several PVC pipes narrow enough to fit just one individual are a shelter alternative, no substrate necessary.
Some Tropheus species and varieties may interbreed, so it is important not to keep more than one type in an aquarium. Other cichlids can be kept with Tropheus, but they have to accept the same food and not bully them. Recommended are small Petrochromis species and goby cichlids (Eretmodus, Spathodus, and Tanganicodus).
For the well-being of Tropheus, the aquarium water should be alkaline and hard, ideally with pH 9.0, but a pH level between 7.5 and 9.0 will suffice. One of the early mistakes of people trying to keep Tropheus was to house them in soft, acidic water, as was the custom for early aquarium keeping.
Another important factor is the temperature, which must be kept between 77° and 81°F (25° and 27°C); warmer water kills Tanganyikan cichlids by decreasing the oxygen content and promoting faster decomposition of food. When introducing your Tropheus to the aquarium, the tank must be fully cycled so no ammonia or nitrites are present, and water changes of 50 percent every two weeks, at minimum, is important to reduce the accumulation of nitrates.
Tropheus feed on filamentous algae in the wild, and their feeding in the aquarium has been one of the tricky parts of their successful keeping. They must be fed mostly with vegetable matter. One of the most popular foods is based on spirulina, either as flakes or tablets. Being careful not to overfeed, several small portions a day can be offered.
In the wild, Tropheus cichlids ingest other small animals when feeding, so it is often recommended to add small crustaceans to their diet; these could be in the form of daphnia, krill, cyclops, or brine shrimp. By all means avoid highly nutritious food, particularly from mammalian origin, or nutritious pellets. Tropheus have not evolved to process animal fat or even very nutritious food.
A common result of failing to comply with these rules results in what is known as “bloat,” a swelling of their internal organs, most of the time with fatal results—a bloated Tropheus is a dead Tropheus. Tropheus come with high price tags, so you want to avoid this from happening.
Once an aquarium colony is formed and territories established—most times by one or two males—it will remain stable. Males will want to spawn with females, and females may not be ready since they take several months to recover from previous spawns. So the females must have shelters in which to take refuge and avoid unwanted attention.
If new specimens are to be introduced into the colony, the whole tank must be rearranged, as otherwise they will not be accepted. Take into consideration, however, that a reestablishing of pecking orders and territories comes with its own problems, since nothing guarantees that the previous hierarchy will be reestablished and that all fish will be accepted.
Taxonomy
The genus Tropheus was diagnosed mainly by the structure of the mouth: “Jaws angularly bent at the sides, with bands of minute tricuspid teeth, an outer row of bicuspid teeth, and enlarged conical teeth at the sides of the premaxilary, mouth transversely linear when closed; maxillary concealed under the praeorbital.”
Of importance is one more feature: Tropheus possess six anal spines, which is a higher number than in the genus Tilapia. In 1986, Poll added to the diagnosis that the genus has a stocky body with a strongly convex snout and head.
The name Tropheus derives from the Greek word trophos, which means nurse, in reference to their mouthbrooding behavior—a mouthbrooding female was among the type specimens.
A Challenging Gem
Those who study cichlids are endlessly fascinated by the social behaviors, interesting habits, and wide variety of beautiful color patterns of the Tropheus. They may be challenging, but a large tank holding a colony of these fish is something you can spend hours watching in awe. It is of little surprise that these treasures from Lake Tanganyika have been longtime favorites of aquarists all around the world, placing them among the ranks of some of the most popular aquarium fish.
