Taxonomy & naming
Mylochromis sp. "Sphaerodon Nkhomo" has no scientific description, no describing author or year, and does not appear in Eschmeyer's Catalog of Fishes or FishBase under its own name. Its trade name follows the standard resemblance-plus-locality convention: "sphaerodon" refers to Mylochromis sphaerodon (Regan, 1922), named for the spherical, ball-like crowns on its middle pharyngeal teeth — a snail-crushing adaptation that gives the species its common name, roundtooth hap; "Nkhomo" identifies this form's collection point at Nkhomo Reef. Mylochromis sphaerodon is documented across several southern-lake localities catalogued separately by field surveys, including Chiofu Bay, Namalenje Island, and Senga Bay, and this Nkhomo Reef form is presented as belonging to the same recognisable type rather than as an independently confirmed identification. No authority or publication date should be attached to it.
Morphology
As a form allied to Mylochromis sphaerodon, this fish is expected to share that species' distinctive build: a deep-bodied, laterally compressed cichlid with a small, rounded head and a notably small mouth relative to its size, immediately setting it apart from the genus's longer-snouted, wider-mouthed piscivorous members. Mylochromis sphaerodon reaches approximately 8 in TL in the field. The diagnostic feature of the species — spherical, molariform crowns on the middle pharyngeal teeth, forming a crushing mill for snail shells — is an internal anatomical trait that cannot be confirmed for this form without examining specimens directly, though its resemblance to sphaerodon in external body shape is the basis of the trade name. Breeding males of M. sphaerodon develop blue body coloration with a yellow anal fin; whether the Nkhomo Reef form shows the same pattern has not been separately documented, though it is a reasonable expectation given the resemblance.
Habitat
The recorded locality for this form is Nkhomo Reef. Mylochromis sphaerodon as a species is restricted to the southern half of Lake Malawi, documented from roughly Kande Island south to Mangochi along the western shore and north to Chuanga in Mozambique along the eastern shore, occupying shallow sandy inshore waters at depths of roughly 16–66 ft. Nkhomo Reef sits within this general southern-lake range. Unlike rocky-shore mbuna, sphaerodon-type Mylochromis do not require boulders or caves; they are fish of open, bare sand where gastropods and buried invertebrates are accessible.
Feeding
Mylochromis sphaerodon is a specialised molluscivore, with stomach content studies showing gastropod remains as the primary dietary component alongside copepods, cladocerans, algae, and midge larva fragments. Its lower pharyngeal bone carries large, rounded, molariform teeth backed by powerful adductor muscles, shaped specifically for cracking snail shells rather than gripping soft prey. This form is presumed to share the same specialised feeding strategy given its resemblance to sphaerodon, though the internal pharyngeal-tooth structure that powers this diet cannot be confirmed externally, and no dedicated study exists for the Nkhomo Reef population specifically.
Mating
Documented field observations of Mylochromis sphaerodon's mating behaviour are limited even for the described species. Breeding males develop blue-and-yellow coloration and move to suitable sandy substrate to display to passing females, following the loosely territorial, non-pair-bonding pattern typical of the genus. The species' small mouth and rounded head suggest it does not hold large rock-based territories as some open-water predators do; instead, it is likely a sand-floor resident with a modest territory. This form is presumed to follow the same pattern, though it has not been separately documented for Nkhomo Reef.
Breeding
Mylochromis sphaerodon is a maternal mouthbrooder, as are all Lake Malawi haplochromines: the female takes fertilised eggs into her buccal cavity after spawning and broods them without feeding for the full incubation period, releasing free-swimming fry once they can fend for themselves. No clutch size has been published specifically for the species; for comparably sized Malawi haplochromines, clutches typically run roughly 20 to 60 eggs, a genus-typical figure rather than a measured value. This form is presumed to follow the same reproductive pattern, with no separate documentation for the Nkhomo Reef population.
In the aquarium
Mylochromis sphaerodon is rarely encountered in the hobby, and this Nkhomo Reef form even more so, with no dedicated husbandry record. Following the described species' requirements, a keeper should provide a large tank of at least 40–65 US gal for a small group, a deep sand substrate of at least 3–4 in to support the fish's substrate-associated foraging, and water matched to Lake Malawi's chemistry: pH 7.8 to 8.6, temperature 75–82 °F, and hard, alkaline water with general hardness in the region of 10 to 20 °dGH. Nitrate should be kept low through regular water changes, and soft or acidic water avoided entirely, as it stresses Malawi haps and increases the risk of bloat. A diet of quality cichlid pellets supplemented with hard invertebrate items suits the sphaerodon-type feeding strategy better than shrimp- or krill-heavy foods intended for piscivores. Tankmates should be other non-aggressive Malawi haps and peacocks rather than combative mbuna.
Conservation
No IUCN Red List assessment exists for Mylochromis sp. "Sphaerodon Nkhomo", and none can until it is formally described. Its described relative, Mylochromis sphaerodon, is assessed by the IUCN as Least Concern, being distributed across the southern half of the lake without major known threats, though the assessment does flag subsistence fishing and aquarium collection as ongoing pressures, and lake-wide warming and catchment sedimentation as longer-term concerns for sandy-shore species that depend on gastropod communities. Whether the Nkhomo Reef form faces comparable or different pressures is not documented. The honest position is that it is unassessed.