Taxonomy & naming
Tropheops sp. "Chilumba" has no formal scientific name, describing author, or Catalog of Fishes entry. It was originally recorded as part of the broader population later named "Pseudotropheus sp. 'tropheops red fin'" by A.J. Ribbink and co-workers in 1983, based on specimens from Ruarwe further south on the Malawian coast. Ad Konings subsequently judged the northernmost population, occurring from Chitande Island to Mphanga Rocks near the town of Chilumba, different enough from the "true" Red Fin population to warrant its own separate trade name, "Ps. sp. 'tropheops chilumba,'" splitting the two informally. Neither form has ever received a validly published description, so no authority or date should be attached to either, and readers should not treat "Chilumba" as simply a locality label for ordinary Red Fin — Konings specifically distinguished the two as different populations.
Morphology
A compact, blunt-headed mbuna on the standard Tropheops build, with the thick lips and closely packed rows of comb-like teeth used to scrape algae from rock, shared with its close relative Tropheops sp. "Red Fin." Because it was split from Red Fin specifically on the grounds of being different enough to warrant a separate name, some distinction from that form's orange-red juvenile/female fin colouration and its intermediate barred-to-orange male colour sequence is implied, but a detailed independently published colour description specific to the Chilumba population, beyond the fact of the taxonomic split itself, is not available for this account.
Habitat
Tropheops sp. "Chilumba" is recorded from a tight cluster of localities on the far northern Malawian shore around the town of Chilumba, including Kaphaso Reef, Luwino Reef, Maison Reef, and Mphanga Rocks, extending north to Mdoka. This is a considerably narrower range than that of the related Red Fin population further south, consistent with the fine-scale, locality-restricted distribution typical of Lake Malawi's rock-dwelling mbuna. It occupies the same rocky, wave-influenced shallow-to-intermediate habitat used by Tropheops generally. Water conditions follow the lake's standard chemistry: warm, hard, and alkaline, with temperature in the mid-20s Celsius and pH on the alkaline side of neutral.
Feeding
Tropheops sp. "Chilumba" grazes aufwuchs from rock surfaces, the standard feeding mode for the genus, using its comb-like outer teeth to scrape the mixed film of algae, diatoms, and associated micro-invertebrates from sunlit rock in the shallow-to-intermediate zone. The aufwuchs itself is not a single food but a whole microhabitat -- filamentous and diatomaceous algae bound up with detritus and the small invertebrates that live within it -- so a grazing mbuna takes in a mixed, protein-and-fibre diet in a single bite rather than pure plant matter. Because algal turf grows fastest where sunlight and wave action are both strong, feeding activity and territorial defence of good grazing patches are concentrated in the same shallow, wave-exposed rock that territorial males also use for breeding, tying the two behaviours to the same stretch of habitat.
Mating
Breeding follows the standard mbuna pattern of male territoriality and female choice, with dominant males holding and defending small rock territories to attract passing females and no pair bond formed. Notably, this form has been specifically documented, through observations attributed to Kapralski in the early 1990s and cited by Ad Konings, as one of a limited number of Lake Malawi cichlids in which at least partial external fertilisation of the eggs occurs — meaning some eggs are fertilised outside the female's mouth during the spawning act itself, rather than exclusively inside it as in the more typical haplochromine pattern. This makes Tropheops sp. "Chilumba" one of the better behaviourally documented undescribed mbuna, even though it has no formal taxonomic description.
Breeding
As in all Lake Malawi cichlids, the female broods fertilised eggs and larvae in her mouth, in this species' case following spawning in which fertilisation has been recorded to occur at least partly outside the female's mouth rather than entirely within it. Brooding lasts roughly three to four weeks before free-swimming fry are released, with no further parental care from either parent. Clutch size has not been documented specifically for this form, but by analogy with similarly sized Tropheops it is likely modest, on the order of a few dozen eggs.
In the aquarium
Tropheops sp. "Chilumba" is kept as a classic northern-lake mbuna, closely resembling its Red Fin relative but maintained separately by keepers who want to preserve the two populations as distinct lines. A rock-dominated tank with a base of fine sand suits it well, with rockwork arranged into distinct piles and clear sightline breaks so a dominant male's territory does not extend across the whole tank. A footprint of at least 47 in is a sensible minimum for a harem group.
Water should mirror Lake Malawi conditions: temperature in the mid-20s Celsius, pH roughly 7.7 to 8.6, and moderately hard to hard water, held stable. As with most mbuna, diet should lean vegetable — a spirulina-based flake or pellet as the staple, with only occasional protein-rich foods, since a high-protein diet is strongly linked to bloat in this group. One male to several females is the standard stocking ratio.
Conservation
Tropheops sp. "Chilumba" has not been evaluated by the IUCN and, as an undescribed form without a formal scientific name, has no Red List assessment of any kind. Its recorded range is a tight cluster of reefs around Chilumba town on the far northern Malawian shore, a narrower distribution than its Red Fin relative and one that leaves it more exposed to concentrated local pressure such as ornamental collecting or nearshore habitat disturbance at any single reef. Captive-bred stock is the more sustainable choice for keepers wanting to maintain this specific line.