Taxonomy & naming
Placidochromis sp. "Phenochilus Metangula" has no describing author and no entry in Eschmeyer's Catalog of Fishes. Its trade name references Placidochromis phenochilus (Trewavas, 1935), the white-lips cichlid described from Vua in Malawi's Karonga District, whose epithet — from Greek phaneros, "conspicuous," and cheilos, "lip" — describes its chalky-pale lips against an otherwise deep blue body. Confirmed P. phenochilus localities lie on the Malawian northwestern shore (Mdoka, Chesese, Chirwa Island); a separate undescribed Tanzanian population, sold as "phenochilus tanzania" or "Star Sapphire," occurs on the eastern shore between Makonde and Lupingu and lacks the diagnostic white lips. This Metangula population, recorded on the Mozambican (Niassa) shore in the west-central lake, is geographically distinct from both, and collectors track it as its own informal field form under the phenochilus trade name based on general resemblance rather than any confirmed identity with either the Malawian or Tanzanian populations.
Morphology
No formal description of this Metangula population's colour pattern or measurements exists, and none is invented here. Described P. phenochilus reaches up to about 6 in total length, with a moderately deep, laterally compressed body and, most distinctively, pale whitish-to-cream lips against continuous, saturated cobalt-blue body colour in adult males; the Tanzanian phenochilus-type population instead shows metallic white blotching rather than pale lips. Whether this Mozambique population carries the true white-lip trait, the Tanzanian-style blotching, or some other pattern has not been documented in the sources available here, and no colour claim is made for it. Genus-typical size for phenochilus-type Placidochromis runs to roughly 4.5–8 in.
Habitat
Metangula is a town on the Mozambican shore of Lake Malawi, in the west-central part of the lake opposite Likoma Island. Described P. phenochilus and its Tanzanian counterpart both occupy open sandy habitat at moderate-to-considerable depth, generally deeper than 49 ft, well below the shallower zones favoured by many other blue sand-dwelling cichlids in the same ecological guild. If this Metangula population shares that ecology, as its trade name suggests, it would occupy similar deep sand habitat off the Mozambican shore; no dedicated depth survey specific to the site has been published to confirm this directly.
Feeding
Described P. phenochilus belongs to a distinctive guild of conspicuously coloured sand-dwelling cichlids that follow larger sand-sifting species, collecting small invertebrates exposed as the host ploughs through the substrate rather than digging for themselves. Placidochromis sp. "Phenochilus Metangula" is presumed to feed in a broadly similar follower-invertivore fashion if it shares that ecology, though no feeding study specific to this Mozambique population has been published.
Mating
No courtship account has been published for this Metangula population. By analogy with described P. phenochilus, males would be expected to establish a temporary territory on open sand and court females with lateral displays, with egg fertilisation occurring in the female's mouth as is typical for Malawian maternal mouthbrooders; some other members of the same blue sand-dweller guild instead fertilise eggs in the open sand, so this point is not certain even for the nominal species. Nothing more specific is asserted for this informal form.
Breeding
Reproduction is expected to be by maternal mouthbrooding, as in all Lake Malawi haplochromines: the female alone collects the fertilised eggs into her mouth and incubates them through hatching, with no paternal care beyond the male's defence of the spawning site. In described P. phenochilus, incubation at aquarium temperatures around 77 °F takes roughly three weeks, after which the female releases fry gradually as she judges the environment safe; clutch sizes are estimated at 20–50 fry per spawn based on the closely related Tanzanian phenochilus-type form kept and bred in captivity. No brood-size or timing figures specific to this Metangula population have been documented in the wild, and wild spawning has not been directly observed even for the better-studied nominal species.
In the aquarium
This Metangula form is not established in the aquarium trade under this name, and no husbandry account specific to it exists. Were it kept, care would follow the general template for phenochilus-type Placidochromis: a large tank of 59 in or more with a fine sand substrate several centimetres deep, rockwork confined to the perimeter, and open swimming space in the centre. Water chemistry should match the Lake Malawi standard — hard and alkaline, pH roughly 7.7–8.6, temperature 75–82 °F — with efficient filtration and substantial weekly water changes, since Malawi cichlids are sensitive to nitrogenous waste and high-protein diets can predispose them to bloat. A diet balancing quality cichlid pellet with modest amounts of small invertebrate-based frozen foods would suit its presumed invertivorous ecology. Phenochilus-type fish are generally considered calmer than many large haplochromines and are best paired with similarly peaceful tankmates rather than aggressive haps or mbuna.
Conservation
Placidochromis sp. "Phenochilus Metangula" has not been evaluated by the IUCN and, as an undescribed form, carries no Red List status. Its close relative P. phenochilus was assessed as Endangered in 2018 owing to its restricted Malawian range and suspected population decline, a reminder that phenochilus-type Placidochromis in general tend to occupy narrow, specific stretches of shoreline rather than ranging lake-wide. This Metangula population, apparently confined to a single Mozambican locality, should be treated with the same caution due any narrow-range Malawi sand-dweller absent a formal assessment, particularly given the general pressures of sedimentation, fishing activity, and shoreline development documented across the lake's cichlid literature.