Taxonomy & naming
Pseudotropheus sp. "Sand Cobalt" is undescribed: no holotype, no publication, no entry in Eschmeyer's Catalog of Fishes. Generic placement follows Pseudotropheus Regan, 1922, provisionally, pending any future revision. The trade name follows the standard two-part convention for Lake Malawi locality forms — a descriptive tag plus a habitat or colour cue — here combining "Sand", indicating the fish favours the sand-adjacent intermediate zone rather than solid rock, with "Cobalt", for a deep saturated blue male colour distinct from the paler powder-blue of some relatives. Likoma Island, where this form is recorded, is also the published type locality of the well-known Chindongo socolofi (the "pindani", described by Johnson in 1974 as Pseudotropheus socolofi), so the island's rocky-to-sandy shore is known to support more than one blue mbuna; "Sand Cobalt" is a separate, distinct, undescribed form and should not be confused with socolofi or its relatives.
Morphology
This form follows the standard elongate, laterally compressed Pseudotropheus body plan, with a moderately sloped forehead and the closely packed dentition used to rasp aufwuchs from rock and rubble. Per its trade name, dominant males are expected to display a deep, saturated cobalt-blue body colour, though the fin trim, any facial markings, and the precise female pattern have not been documented in detail in the sources available here, so no complete colour description is asserted. Genus-typical adult length runs roughly 3–4.5 in, males somewhat larger than females.
Habitat
Pseudotropheus sp. "Sand Cobalt" is recorded from Likoma Island, a substantial island roughly in the middle of Lake Malawi that lies within Mozambican waters but is administratively Malawian territory, and whose surrounding shore mixes rock outcrops with stretches of open sand. Its trade name suggests it favours the intermediate zone — scattered rock and rubble over a sandy bottom — rather than the dense boulder piles preferred by strict rock specialists, a niche shared by several other Malawi mbuna that forage over open ground while still relying on rock for shelter and spawning sites. Water chemistry follows the Lake Malawi norm: warm, hard and alkaline, typically 75–82 °F and pH 7.7–8.6, with this intermediate habitat generally sitting in the 13–49 ft depth band documented for similar sand-adjacent mbuna elsewhere on the lake.
Feeding
As with other Pseudotropheus, this form is presumed to graze aufwuchs — the mixed mat of filamentous algae, diatoms and small invertebrates coating rock and rubble — but a sand-adjacent lifestyle, as its trade name implies, may also bring it into contact with the looser biofilm and detritus that settles over open sand, a resource some intermediate-zone mbuna pick at alongside rock-bound algae. No feeding study specific to this population exists, so this account draws on the general biology of algae-grazing mbuna rather than direct observation.
Mating
Breeding behaviour is presumed to follow the standard mbuna pattern: polygynous and territorial, with a dominant male holding a patch of rock or rubble at the sand-rock interface and displaying his cobalt-blue colour to attract passing females rather than pairing exclusively. No behavioural documentation specific to "Sand Cobalt" exists, and this account follows the well-established pattern for Pseudotropheus generally rather than direct observation of this population.
Breeding
Pseudotropheus sp. "Sand Cobalt" is a maternal mouthbrooder, as is the entire genus. After spawning, the female takes the fertilised eggs into her mouth and incubates them for roughly three to four weeks, feeding little during that period, before releasing free-swimming fry that receive no further parental care. Clutch size has not been documented for this population; genus-typical Pseudotropheus of comparable size produce clutches in the range of a few dozen eggs.
In the aquarium
Pseudotropheus sp. "Sand Cobalt" should be kept as a standard intermediate-zone mbuna. A tank of at least 47 in should combine scattered rockwork — enough to give a territorial male a defensible patch and offer females cover — with open sand for the fish to range over, mirroring its natural sand-adjacent habitat rather than the solid boulder wall used for pure rock specialists. Water chemistry should replicate Lake Malawi: 75–82 °F, pH 7.7–8.6, consistently hard and alkaline. Diet should be predominantly vegetable-based — a spirulina-forward flake or pellet as the staple — since high-protein foods are poorly tolerated by algae-grazing mbuna and are strongly implicated in Malawi bloat. Keep a surplus of females per male, and avoid housing it with other deep-blue mbuna from the same Likoma Island shore where visual confusion or hybridisation risk is higher.
Conservation
No IUCN Red List assessment exists for Pseudotropheus sp. "Sand Cobalt", and none can while it remains formally undescribed; no status, category or year should be attached to it. As a mbuna apparently restricted to a single island's shore, it carries the general vulnerability shared by narrow-range mbuna around Lake Malawi — dependence on a limited stretch of intact intermediate habitat and exposure to localised over-collection for the ornamental trade — but no population-specific study documents its actual abundance or trend. The accurate statement is that it is unevaluated.