Taxonomy & naming
The species was described in 1984 by the German aquarists Manfred K. Meyer and Wolfgang Foerster, in the Revue française d'Aquariologie et Herpétologie, as Pseudotropheus greshakei — the paper appeared in the journal's 1983 volume but was issued in 1984, which is why the authority is conventionally dated to that year. The original material came from Makokola, on the southeastern branch of Lake Malawi (then often called Lake Nyasa); Eschmeyer's Catalog of Fishes records the holotype as SMF 17846 in the Senckenberg Museum, Frankfurt, with paratypes split between Senckenberg and the Natural History Museum, London (BMNH 1984.3.26.1). For more than a decade the fish sat in the catch-all genus Pseudotropheus, the holding pen for most blue-black 'zebra' mbuna. That changed with Stauffer, Bowers, Kellogg and McKaye's 1997 revision of the Pseudotropheus zebra complex, which erected the new genus Metriaclima for the rock-dwelling zebras and reassigned greshakei to it as Metriaclima greshakei. A parallel name, Maylandia Meyer & Foerster 1984, had been raised in the very same original paper; under the rules of priority Maylandia is the senior synonym of Metriaclima, and the Catalog of Fishes therefore treats Maylandia greshakei as the valid combination — though many hobby and scientific sources, including the Cichlid Room Companion, continue to use Metriaclima. The two names refer to the same fish; the choice between them is a nomenclatural preference, not a disagreement about identity. The species belongs to the mbuna, the rock-dwelling, algae-grazing radiation of Lake Malawi haplochromines, and within Maylandia it is a close relative of the look-alike Maylandia mbenjii of Mbenji Island; unlike mbenjii, greshakei shows no OB (orange-blotch) polymorphism.
Morphology
This is a medium-small, robust mbuna with the deep, laterally compressed, fusiform body typical of the zebra group. FishBase gives a maximum of 5.5 in total length, drawn from the Stauffer revision; in the field, malawi.si reports wild males reaching about 5.5 in and females around 4 in total length, while well-fed aquarium males can push to 6.5 in or more. The fin counts are those of a zebra-type Maylandia: 17–18 dorsal spines with 8–9 soft rays, and three anal spines over 6–7 soft rays. What sets greshakei apart is its colour, and specifically the way the sexes are coloured. In most mbuna the dominant male is the gaudy one and the female drab; greshakei keeps that contrast but recasts it. Territorial, breeding males turn a clean cobalt- to ice-blue over the whole body and head — the 'ice blue' of the trade name — capped by a bright orange to orange-red dorsal fin, sometimes with faint darker bars showing through the blue. Females, juveniles and non-territorial males are a plain light grey-brown to sandy fawn, but they too carry a yellow-to-orange dorsal fin, so the orange flag is shared by both sexes while the blue body is the male's alone. This shared orange dorsal over a strongly sex-linked body colour is the species' diagnostic signature and the easiest way to tell it from other southeastern-arm zebras.
Habitat
Maylandia greshakei is a lacustrine endemic — found only in Lake Malawi, and within the lake only at Makokola Reef in the far southeastern arm, off the shore near the Club Makokola resort in the Mangochi district. This is one of the most restricted ranges of any commonly kept cichlid; the fish has never been reliably recorded at any other locality. It lives in the rocky biotope, but a particular kind of rocky biotope: the rocks here are permanently coated with a layer of fine sediment rather than scrubbed clean by surf, and greshakei stays closely associated with large rocks that provide both shelter and spawning caves. FishBase records a depth range of about 49–115 ft, with malawi.si placing the bulk of the population over roughly 49–98 ft — deeper than many shallow surf-zone mbuna, consistent with a fish of sediment-rich rather than wave-washed rock. In-situ chemistry has not been published for this exact reef, but it falls within Lake Malawi's well-characterised surface envelope: warm, hard and strongly alkaline, with temperatures broadly in the mid-20s Celsius (FishBase cites about 75–79 °F) and a pH that runs from roughly 7.7 to 8.6 across the upper water column. The southeastern arm is a shallow, productive sector of the lake, and the sediment film that defines greshakei's reef is part of what feeds the algal and planktonic productivity it depends on.
Feeding
Like the mbuna generally, greshakei is built around grazing the aufwuchs — the felt of algae, diatoms and the small invertebrates living within it that coats submerged rock — and its teeth and gut are those of a herbivore-detritivore (FishBase places it near the base of the food web, at a trophic level of about 2.0). But the species splits its feeding between two zones depending on social rank. Territorial males, tied to their patch of rock, feed mainly from the biocover on the stones, scraping the sediment-rich algal layer in place. Non-territorial fish — females and subordinate males not bound to a cave — spend much of their time in open water above the reef, feeding on phytoplankton and other plankton drifting in the column. This split between rock-grazing residents and plankton-picking wanderers is a recurring theme among the deeper, sediment-zone mbuna and lets the population exploit both the fixed algal crop on the rocks and the suspended productivity of the water above them. In the community it is a mid-level grazer rather than a predator, harmless to other fish and part of the dense mbuna guild that keeps the lake's rock surfaces cropped.
Mating
Maylandia greshakei is a polygynous, lek-style breeder with no lasting pair bond, the standard mbuna arrangement. Mature males establish and defend territories centred on a cave or sheltered recess among the large rocks, and it is the act of holding a territory that switches a male into full breeding dress — the cobalt body and flaring orange dorsal that advertise his quality to passing females and warn off rival males. Females are not territorial; they occur singly or move over the reef in loose foraging schools, visiting males' caves to spawn. For an mbuna the species is described as relatively peaceful, with aggression directed chiefly at conspecific males and intensifying during the breeding period rather than spilling broadly across the community. The bright dorsal fin shared by both sexes, set against the male's exclusive blue body, is the visual machinery of this system: the male's colour signals status and readiness, while the female's plain body keeps her cryptic as she shuttles between feeding in open water and spawning in the rocks.
Breeding
Reproduction follows the maternal mouthbrooding pattern that defines the Lake Malawi haplochromines, and which FishBase records for greshakei as well (the species is listed as oviparous). A receptive female enters a territorial male's cave, and the pair circle in the classic mbuna spawning routine: she lays a small batch of eggs, immediately turns to take them into her mouth, and is drawn to nip at the egg-spot markings (ocelli) on the male's anal fin — at which point he releases milt and the eggs are fertilised inside her buccal cavity. She then carries the developing eggs and larvae in her mouth, fasting through much of the period, for roughly three to three-and-a-half weeks before releasing a brood of free-swimming fry. Clutch size has not been formally published for the species, but Maylandia of this size class typically carry on the order of a few dozen eggs — a small clutch traded for the protection of oral incubation. There is no biparental care: the male's role ends at fertilisation, and once the female releases the fry she gives no further care. The combination of cave-spawning, modest clutch and a long, mouth-bound incubation makes greshakei a straightforward and reliable breeder in captivity, which is much of why the Ice Blue became an established hobby fish despite its pinpoint wild range.
In the aquarium
Maylandia greshakei is a well-established and moderately easy mbuna for the experienced cichlid keeper — popular enough that captive-bred stock is routinely available, sparing the wild single-reef population any collection pressure. A group of one male with three or more females works well in a tank of at least 47 in (roughly 55–65 US gal); the extra footprint is not decorative indulgence but a practical buffer for the male's territorial aggression. Like all mbuna, greshakei is highly driven to defend space, and a tank that is too small concentrates that aggression fatally on the females. As a generalisation true of zebra-group Maylandia, males kept with fewer females than they can spread attention across will batter a single female until she stops feeding and eventually dies.
The aquascape should replicate the Makokola Reef biotope in the basics: a deep sandy substrate (Lake Malawi sand or fine washed silica), substantial piles of smooth or rounded rocks stacked to form caves and overhangs, and open swimming space in the foreground. Plants are not part of this fish's world and are generally unnecessary; if added, they will likely be uprooted or ignored. The water must be hard and alkaline to match Lake Malawi conditions: pH 7.8–8.6 and moderately hard to hard (10–20 °dH is a practical target), temperature 75–79 °F (facts.water). Malawi salt mixes or dolomite gravel can raise hardness and carbonate buffering in soft-water tap supplies. Filtration should be robust — mbuna produce heavy biological load — and regular partial water changes of around 25–30% weekly are the single most effective disease-prevention measure.
Compatible tankmates are best chosen from other similarly sized mbuna or from robust, rock-dwelling haplochromines of comparable aggression. Mixing with very small or very passive fish is asking for trouble; mixing with much more aggressive species can suppress greshakei males enough to compromise their colour and condition. Species from different Malawi rock biotopes — Labidochromis caeruleus, other Maylandia species of similar size, Pseudotropheus acei — are frequently mixed with reasonable success, though any mbuna community requires the keeper to watch for individuals that are being singled out and to rearrange rocks if the social dynamic sours. Do not mix with open-water Malawi haps that need vastly different territories, and never mix with soft-water Amazonian cichlids or other fish that cannot tolerate hard alkaline chemistry.
Diet is where many keepers go wrong with this species and with mbuna generally. Maylandia greshakei is an aufwuchs grazer whose gut is adapted to process high volumes of algae and plant matter at a low trophic level. Feeding it the high-protein cichlid pellets or frozen bloodworm diets intended for piscivorous or insectivorous cichlids is a common and serious error. Excess animal protein is widely linked to 'Malawi bloat', a rapid-onset, often fatal condition (thought to involve opportunistic flagellate or bacterial proliferation in a gut not equipped to handle the protein load) that presents as distension, loss of appetite, and rapid decline. The bulk of the diet — 70–80% or more — should be spirulina-based or other vegetable-heavy flake or pellet; occasional small offerings of brine shrimp or mysis are acceptable, but bloodworm should be avoided. This is not a difficult dietary requirement once understood; it is simply the opposite of what most newcomers assume cichlids need.
Breeding in the aquarium is straightforward and happens without special intervention once the group is settled, well-fed, and housed correctly. The male will excavate or clear a preferred cave; spawning follows the sequence described in the Breeding section, and the female will hold for roughly three weeks. She should ideally be moved to a dedicated holding tank before she releases the fry, both to protect the fry from being eaten by tankmates and to allow the female to recover condition undisturbed before returning to the main tank. Fry are large enough at release to take crushed spirulina flake immediately. Maylandia greshakei breeds readily enough in captivity that it poses no challenge to the patient keeper, and its distinctive cobalt-and-orange colouring makes it a rewarding display fish even when not breeding.
Conservation
The IUCN Red List assesses Maylandia greshakei (under the name Metriaclima greshakei) as Near Threatened, assessed on 11 June 2018 by Ad Konings — an upgrade from the 2006 listing of Vulnerable. The category turns entirely on the species' extreme narrow endemism: known from a single reef, it qualifies on range-size criteria (B1a+2a) for a threatened or near-threatened listing regardless of how healthy the population itself is. And the population does appear healthy. Konings notes that the fish remains common at Makokola Reef because it is not targeted by local fishermen — it is small and difficult to net among the rocks — and argues that, barring a natural disaster that destroyed the reef, the species would arguably warrant Least Concern; the conservative listing reflects the inherent fragility of any single-site endemic rather than an observed decline. That species-level picture sits inside a lake under real and mounting strain. Lake Malawi holds one of the planet's richest freshwater fish faunas, on the order of 800-plus cichlid species, and the basin review by Chavula and colleagues (2023, Journal of Great Lakes Research) documents rising sediment and nutrient loading off deforested catchments, shoreline degradation, surface warming with stronger stratification, and heavy fishing pressure on inshore stocks. For a fish whose entire world is one sediment-coated reef, the threat that matters most is local and specific: any event — heavy sedimentation from catchment erosion, shoreline development, a pollution incident — that degraded Makokola Reef would imperil the global population at a stroke. The honest summary is that Maylandia greshakei is not currently declining, but its single-point distribution leaves it with no margin, and the basin-wide pressures the lake faces are exactly the kind that a one-reef endemic cannot absorb.