Taxonomy & naming
Gephyrochromis sp. "Yellow" has no authority, no year of description, and no FishBase page, because no taxonomist has published a formal account of it. It circulates only under this informal field name, taken directly from its most obvious character, following the open-nomenclature convention used throughout Lake Malawi's cichlid literature: genus, "sp.", and a descriptive tag in quotation marks. Gephyrochromis itself is a small genus — George Boulenger described the type species, G. moorii, in 1901, and Geoffrey Fryer added G. lawsi in 1957 — and Mbamba Bay in particular has yielded more than one additional, separately named field form, a reminder of how fine-grained the diversity hiding under "Gephyrochromis sp." really is. This form has not been assigned to either described species and should not be treated as a synonym of one, nor assumed identical to any other Mbamba Bay Gephyrochromis form recorded under a different trade name.
Morphology
Described Gephyrochromis are small, moderately elongate cichlids reaching roughly 4.5–5 in total length at most, built with the genus's diagnostic slender, comb-like outer teeth suited to combing loose sand and periphyton rather than the stouter dentition of rock-grazing mbuna. "Yellow" is named directly for its colour — a predominantly yellow body, the field mark that separates it from the genus's more typical blue-grey, slate, or violet-toned described and undescribed relatives. Beyond that defining colour, no detailed published description exists for this form: the extent and shade of the yellow, any secondary markings, and how males and females differ have not been documented in the sources available to this article, so this account limits itself to what the trade name actually establishes rather than inventing further detail.
Habitat
This form is recorded from Mbamba Bay, on the southern Tanzanian shore of Lake Malawi. Gephyrochromis as a genus favours open sandy ground at or near rocky reefs rather than bare rock itself — Gephyrochromis moorii lives in small mixed-sex groups combing loose sediment, sometimes at real depth, while Gephyrochromis lawsi occupies the transitional zone where steep rock gives way to sand, typically in the range of roughly 13–82 ft. No depth or micro-habitat figure specific to this Mbamba Bay population has been published, so the range given here reflects that genus-typical envelope rather than a documented number. Water conditions follow Lake Malawi's usual hard, alkaline inshore chemistry.
Feeding
The genus Gephyrochromis contains two documented feeding modes: Gephyrochromis moorii combs loose sand and its periphyton coating with comb-shaped teeth, while Gephyrochromis lawsi feeds chiefly on loose aufwuchs and small invertebrates at the rock-sand interface. No feeding study exists for "Yellow" specifically, so its exact mode cannot be stated as documented fact; given its likely sand-association it plausibly falls into one of these two genus-typical strategies, presented here without further precision than that.
Mating
Reproductive behaviour has not been documented for this form. By analogy with its described relatives, Gephyrochromis males are understood to be weakly territorial rather than strongly site-defending, foraging and courting within loose mixed-sex groups rather than holding a fixed rock territory the way typical mbuna do. Whether "Yellow" follows that same loose social pattern, and any courtship detail specific to it, have not been recorded in the sources available to this article.
Breeding
As with every Lake Malawi cichlid, Gephyrochromis sp. "Yellow" is presumed to be a maternal, ovophilous mouthbrooder: the female takes fertilised eggs into her mouth and incubates them for roughly three weeks before releasing free-swimming fry, with no further parental role from the male. No clutch size or brood duration specific to this form has been published; in the better-studied Gephyrochromis lawsi wild clutches run roughly 25-40 fry, offered here as genus-typical context rather than a documented count for "Yellow."
In the aquarium
Gephyrochromis sp. "Yellow" is a rarely traded, specialist form; even the two formally described Gephyrochromis species are far less commonly kept than the mainstream mbuna, and an undescribed Mbamba Bay field form is scarcer still. A keeper who obtained it should replicate the genus's sand-associated habitat: a generous open sand floor with modest rockwork for shelter rather than a solid rock wall, and Lake Malawi's standard hard, alkaline water chemistry, roughly 75–82 °F and pH 7.7-8.6. Given the genus's mixed feeding habits, a varied diet combining spirulina-based flake with occasional small invertebrate foods is a sensible default. No species-specific husbandry record exists for "Yellow," and general Gephyrochromis practice is offered here only as a starting point.
Conservation
Gephyrochromis sp. "Yellow" has no IUCN Red List assessment, since formal evaluation requires a validly published scientific name and none exists for this form. The genus's two described relatives are both assessed Least Concern, but that status cannot be extended to this undescribed population. As a sand-associated cichlid apparently restricted to a stretch of the southern Tanzanian shore, it shares the general exposures documented across Lake Malawi's inshore cichlid fauna — sedimentation from catchment disturbance, incidental beach-seine bycatch, and the ornamental collecting that targets narrow-range, colourful Malawi endemics — but no population-specific data exist to characterise its status beyond that general context.