Taxonomy & naming
G. Bell-Cross described the species in 1975 as Haplochromis greenwoodi, in a revision of central African Haplochromis published in the Occasional Papers of the National Museums and Monuments of Rhodesia. The type locality is the Okavango River; the holotype (BMNH 1910.5.31.53) and a paratype are old Natural History Museum specimens, and the description also drew on more recent material, including 97 skeletons. The Check-list of the Freshwater Fishes of Africa (Skelton & Teugels 1991) listed it in Serranochromis, and Skelton's 1993 guide to southern African fishes treats it in Sargochromis, the genus Regan erected in 1920, whose members are known in southern Africa as 'happies'. Eschmeyer's Catalog of Fishes follows that placement, citing Skelton (1993, 2001, 2019), Marshall (2011) and Bruton et al. (2018). The Catalog treats Chromys frederici Castelnau, 1861, described from Lake Ngami with no surviving types, as a nomen dubium in its synonymy.
The original combination causes a real mix-up. Seehausen and Bouton named a Lake Victoria rock cichlid Neochromis greenwoodi in 1998, and because FishBase and GBIF file that fish under Haplochromis, both species can appear as 'Haplochromis greenwoodi' in databases and the literature. They are different animals from different basins, and only the Okavango fish is Sargochromis greenwoodi.
Morphology
FishBase, after Skelton (1993), gives a maximum length of 12 in standard length, which makes it one of the larger cichlids in its range. Beyond size, published morphological detail is sparse in accessible sources, and the original description by Bell-Cross remains the primary reference for its diagnostic characters. The IUCN uses the English name deepcheek bream. No measured account of colour, sexual dimorphism or meristics is summarised here, since none could be confirmed.
Habitat
The species lives in the Okavango River, the upper Zambezi and the Kafue River, in Namibia, Zambia and Botswana, and FishBase also notes a report from the Kunene. GBIF holds records from Botswana, Zambia, Angola and Namibia. It is described as uncommon throughout. It prefers still or slow-flowing water with dense vegetation: the backwaters, lagoons and weedy margins of these floodplain rivers rather than open main-channel current. These Kalahari-basin floodplain waters are warm, soft and close to neutral; no in-situ chemistry has been published for this species specifically.
Feeding
FishBase records it feeding mainly on insects, small snails and other invertebrates, occasionally taking small fish, and gives a trophic level of about 3.7. That makes it more of a general invertebrate predator than the specialised mollusc-crushers among its congeners, though snails are part of the diet.
Mating
Field accounts of courtship are not available for this species. FishBase classes it as agamous, meaning no lasting pair bond is formed, and the female carries the eggs, the pattern shared by the mouthbrooding serranochromines of the region.
Breeding
Sargochromis greenwoodi is a maternal mouthbrooder: the female incubates the eggs in her mouth and the male gives no brood care. Breeding takes place in summer (FishBase, after Skelton 1993). Clutch size and fry development have not been published for this species.
In the aquarium
There is no aquarium literature for this species, and it does not appear in the ornamental trade; it is a subsistence and angling fish. Its size alone, up to 12 in SL, would put it beyond most home aquaria, and nothing is known of its behaviour in captivity.
Conservation
The IUCN Red List assesses Sargochromis greenwoodi as Least Concern, in an assessment by D. Tweddle dated 1 March 2007. That assessment is now old. The species is uncommon across a wide range, is taken in subsistence fisheries and by anglers, and FishBase rates its vulnerability to fishing as moderate. No species-specific threats are documented in the sources consulted.