Taxonomy & naming
Aulonocara sp. "Brown Black-pelvic" 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 aquarium and field literature, principally through the work of Ad Konings in his Malawi cichlid books and on the Cichlid Room Companion. The placeholder name follows the standard convention for undescribed cichlids — the genus Aulonocara, the abbreviation "sp." (species), and a descriptive name in quotation marks, here "Brown Black-pelvic," combining the overall brownish tone of the fish with the diagnostic black pelvic fins of the males. Konings places it firmly within Aulonocara on anatomical grounds, since it carries the genus's diagnostic enlarged cephalic sensory pores — the widened lateral-line canals of the head that define the peacocks. It belongs to the assemblage of sand-dwelling peacocks of the western lake, several of which are distinguished only by subtle colour and fin characters and circulate as descriptively named undescribed forms. Until a formal revision is published it should be regarded strictly as a Konings-recognised undescribed form, and no authority or date should be attached to it.
Morphology
This is a medium-sized peacock on the standard Aulonocara plan: a moderately deep, laterally compressed haplochromine body carrying the genus's characteristic head, in which the lateral-line canals of the face are widened into conspicuous sensory pits. Field and hobby references place mature males at roughly 4.5–5 in and females somewhat smaller, the usual peacock arrangement in which males run a little larger. Sexual dichromatism is present. The features that name the form are the overall brown ground colour, more subdued than the bright blue and yellow peacocks, and the conspicuously black pelvic fins of breeding males — a fin character that, together with the muted body colour, separates it by eye from related sand-dwellers. Females and subordinate males are plainer still, silvery-brown and cryptically marked, without the black pelvics. Because the form is undescribed, the working distinction rests on the Nkhata Bay locality together with the brown colour and black-pelvic-fin character of the males.
Habitat
Aulonocara sp. "Brown Black-pelvic" occurs on the western shore of Lake Malawi, documented from the Nkhata Bay area. Its biotope is the classic Aulonocara intermediate habitat — scattered rocks standing on an open sandy floor, the transitional zone the peacocks favour, rather than continuous rock or pure sand. The water is the warm, hard, strongly alkaline medium typical of Lake Malawi's upper and middle water column: temperatures broadly in the mid-20s Celsius, pH on the alkaline side of neutral, and moderately hard to hard general hardness. Like most sand-associated peacocks it forages over the open sand between and around the scattered rocks, in the moderate depths typical of the western-lake peacocks. As an undescribed, locality-based form its full distribution beyond the Nkhata Bay coast is uncertain.
Feeding
Aulonocara sp. "Brown Black-pelvic" is a sand-sifting micro-invertivore, feeding in the manner that defines the peacock radiation. It hovers just above the open sand and holds still, the enlarged sensory pores on its head — part of the ampullary lateral-line system — registering the faint vibrations of small invertebrates moving within the substrate. When prey is detected the fish darts down, takes a mouthful of sand, sifts out the edible items, and expels the spent grains through the gills and mouth. The diet is the genus-typical menu of small benthic invertebrates: insect larvae, micro-crustaceans, and other soft-bodied animals living in the sediment. This sensory, bottom-oriented hunting mode ties the fish to clean, invertebrate-rich sand and is shared across the sand-dwelling peacocks of the western lake to which the form belongs.
Mating
Like all Lake Malawi peacocks, Aulonocara sp. "Brown Black-pelvic" is understood to be polygynous and lek-like in its social organisation, with no pair bond. Males in nuptial colour establish and defend small territories on or near the sandy floor, each centred on an excavated pit or a sheltered spot among scattered rocks, and display from these sites to passing females — the black pelvic fins likely figuring in the display. Females are not territorial; they move across the substrate singly or in loose groups and visit the displaying males. A ripe female approaches a colour-holding male at his site, and courtship follows the conventional haplochromine pattern of lateral display and quivering that leads the female to spawn. The specific details of this form's wild reproduction have not been separately documented, since it is an undescribed population understood chiefly by analogy with related sand-dwelling peacocks.
Breeding
Aulonocara sp. "Brown Black-pelvic" is a maternal mouthbrooder, as are all Lake Malawi peacocks. After a male's courtship draws a willing female to his spawning site, she deposits a small batch of eggs and immediately takes them into her mouth; she is then drawn to the egg-spot markings on the male's anal fin and, in attempting to gather these false "eggs," takes in milt that fertilises the clutch already held in her buccal cavity. The female broods the eggs and larvae in her mouth for roughly three to four weeks, ceasing to feed for most of that period, before releasing free-swimming fry; there is no biparental care and no further parental investment once the young are released. Clutch size has not been documented specifically for this form, but by analogy with similarly sized peacocks it is expected to be modest, on the order of a few dozen eggs.
In the aquarium
Aulonocara sp. "Brown Black-pelvic" is an uncommon, subtly coloured locality form rather than one of the showy line-bred peacocks, and it appears in the trade only sporadically. When it is kept, its requirements follow the general template for an open-sand Lake Malawi peacock.
The tank should provide a fine sand substrate — at least 2 in deep — over a generous open footprint, since this is a sand-sifting fish that needs room to hover and forage; coarse gravel inhibits the sifting behaviour and can damage the gills. A footprint of at least 47 in is a sensible minimum, with a background of stacked rock providing broken sightlines and a few bolt-holes while leaving most of the floor open. Water chemistry should mirror Lake Malawi's water column: temperature in the mid-20s Celsius, pH on the alkaline side of neutral (roughly 7.7 to 8.6), and moderately hard to hard general hardness. Prolonged exposure to soft or acidic water causes chronic problems in Malawi cichlids and should be avoided.
Because males are in nuptial colour and willing to spawn, a single male with several females is the standard, lowest-stress arrangement; a lone male in a bare tank will harass unreceptive females, so generous space and broken sightlines matter. Diet should be the usual varied peacock menu — a quality cichlid pellet or flake as a staple, supplemented with small frozen or live invertebrates such as chironomid larvae, brine shrimp, and daphnia. Fatty foods should be avoided, as they predispose Malawi cichlids to bloat, and regular partial water changes keep nitrate low. Because the form is distinguished by subtle characters, keepers should keep it apart from similar sand-dwellers when breeding to preserve its identity.
Conservation
Aulonocara sp. "Brown Black-pelvic" has not been evaluated by the IUCN, and because it is an undescribed form without a formal scientific name it has no Red List assessment of any kind — no status, no category, no published criteria. That absence is a statement about taxonomy, not about safety. As a locality-based western-shore form it is exposed to the same general pressures as other Lake Malawi cichlids: ornamental collection, inshore habitat disturbance around Nkhata Bay, and the broader stresses of sedimentation and fishing across the basin. No fabricated conservation status should ever be attached to it. The honest statement is simply that it is unassessed and that its true range and status remain to be established by formal study.