Taxonomy & naming
Pseudotropheus sp. "Lucerna Blue Tanzania" is not a formally described species. It has no scientific name of its own, no describing author, no year of publication, and no entry in Eschmeyer's Catalog of Fishes, because no taxonomist has published a description establishing it. It is an informal taxon recognised in the field and aquarium literature, principally through Ad Konings's documentation of Lake Malawi's Mozambican and Tanzanian shores. The placeholder name follows the standard convention for undescribed cichlids: the genus Pseudotropheus, the abbreviation "sp." (species), and descriptive tags in quotation marks, here "Lucerna" (Latin for lamp/lantern), "Blue" for its colouration, and "Tanzania" for its northern collection locality at Undu Reef; the same trade name is also documented at Chiwindi, further south on the Mozambican shore. Pseudotropheus in its modern, narrow sense (following the splitting-off of Maylandia/Metriaclima, Tropheops, Cynotilapia, and other former Pseudotropheus species into separate genera) remains a genus of robust-bodied rock-dwelling mbuna. Until a revision addresses this population directly it should be treated strictly as a Konings-recognised undescribed form, and no authority or date should be attached to it.
Morphology
Pseudotropheus in its modern sense comprises robust-bodied, moderately elongate mbuna with a blunt head and comb-like unicuspid teeth for algae grazing. Genus-typical adult size runs roughly 3–4.5 in; no formal measurement exists for this population specifically. Consistent with its trade name, breeding males are understood to show blue body colouration; no further pattern detail — barring, spotting, or fin colour — is documented for this population in accessible references, so none is asserted beyond the blue ground colour implied by the name. Females and subordinate males are expected to be plainer, in the typical mbuna pattern of duller, more cryptic non-dominant colouration.
Habitat
This form is documented from two localities at opposite ends of the lake: Chiwindi, on the Mozambican shore in the south, and Undu Reef, on the Tanzanian shore in the far north. Whether these represent a single widely disjunct population or two separately named, similarly coloured forms grouped under one trade name has not been established here; both localities are reported as given in the underlying source. As with other Pseudotropheus, the form is expected to be strictly rock-associated, grazing algal films from rock surfaces in the shallow-to-moderate depths typical of mbuna habitat. The water column at both sites follows the lake-wide profile: warm, alkaline, and well-buffered, broadly mid-20s Celsius with pH on the alkaline side of neutral.
Feeding
Pseudotropheus as a genus are specialised algae grazers, using comb-like unicuspid teeth arranged in tight rows to scrape algal films and the associated small invertebrates ("Aufwuchs") from rock surfaces in well-lit water — a feeding style that ties the whole genus tightly to hard, sunlit substrate rather than sand or open water. At both Chiwindi and Undu Reef, the fish would be expected to graze the same kind of algae-covered rock faces documented for mbuna generally around the lake, competing for feeding territory with the dense, mixed mbuna communities typical of these rocky sites. No feeding study exists for this population specifically, but this genus-typical herbivore/detritivore mode is the reasonable characterisation absent contrary data.
Mating
Like other Lake Malawi mbuna, this form is presumed polygynous, with males holding and defending small territories on the rock face, courting passing females from these sites while driving off rival males. There is no pair bond. Females move between male territories, choose largely on colour and site quality, and spawn briefly on the rock before departing with the fertilised clutch in the mouth. No behavioural study specific to this undescribed population exists; the account follows the general pattern documented for Pseudotropheus and rock-dwelling mbuna more broadly.
Breeding
Pseudotropheus sp. "Lucerna Blue Tanzania" is a maternal mouthbrooder, as are all Lake Malawi mbuna. After spawning on the rock face, the female carries the fertilised eggs in her mouth for roughly three weeks, feeding little during this period, before releasing free-swimming fry with no further care from either parent. Clutch size has not been documented for this form specifically; by analogy with similarly sized Pseudotropheus species, a modest clutch — likely a few dozen eggs — is a reasonable expectation rather than a measured fact.
In the aquarium
Pseudotropheus sp. "Lucerna Blue Tanzania" is an uncommon aquarium fish, traded mainly through specialist importers. Where it is kept, husbandry follows the well-established mbuna template.
Dense, stable rockwork built directly on the tank floor is essential, since this is a strictly rock-associated grazer needing abundant surface area and shelter. A footprint of at least 47 in suits an adult group. Water chemistry should mirror Lake Malawi's profile: temperature in the mid-20s Celsius, pH roughly 7.7–8.6, and well-buffered water, with prolonged soft or acidic conditions avoided. Diet should emphasise vegetable matter — a good spirulina-based flake or pellet as the staple, with algae wafers and blanched vegetables as supplements — reflecting its herbivore/grazer biology; protein-heavy foods should be limited, as herbivorous mbuna are prone to digestive problems on rich diets. As with other mbuna, males are territorial and often aggressive, so a single male with multiple females and adequate rockwork to break sightlines works better than a pair in a small tank. Because the two documented collection points are geographically distant, keepers who want to preserve locality-specific provenance should record and keep separate any Chiwindi versus Undu Reef stock.
Conservation
Pseudotropheus sp. "Lucerna Blue Tanzania" has not been evaluated by the IUCN, and as an undescribed form without a formal scientific name it has no Red List assessment of any kind. That silence is a statement about taxonomy, not about safety. Populations at both Chiwindi and Undu Reef face the general pressures affecting Lake Malawi's less-intensively-surveyed Mozambican and northern Tanzanian shores: ornamental collection and the broader basin-wide stresses of sedimentation and fishing pressure. No conservation status should be fabricated for it. The honest statement is that it is unassessed and that its true range and status remain to be established by formal study.