Taxonomy & naming
Pseudotropheus sp. "Tiny" 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 "Tiny" is a straightforward size descriptor, distinguishing this form from other, larger Pseudotropheus at the same locality; small adult size relative to typical mbuna is not unusual in the genus and its relatives — a pattern that shows up in several dwarf mbuna lineages around the lake — but no formal comparison against co-occurring species has been published for this specific population.
Morphology
This form follows the standard laterally compressed Pseudotropheus body plan, with a moderately sloped forehead and the closely packed dentition used to rasp aufwuchs from rock, but per its trade name it is expected to reach a smaller adult size than typical genus members — plausibly in the 2.5–3 in range rather than the 3–4.5 in more usual for Pseudotropheus, though this figure is an inference from the name rather than a measured value. Colour and any sexual dichromatism have not been documented in detail in the sources available here, so no specific pattern is asserted as confirmed.
Habitat
Pseudotropheus sp. "Tiny" is recorded from Thumbi West Island, a rocky island within Lake Malawi National Park at Cape Maclear on the southern Malawian shore — a UNESCO World Heritage Site protected specifically for its exceptional cichlid diversity, and one of the most heavily studied and dived stretches of the lake's shoreline. Like other rock-dwelling Pseudotropheus it is expected to hold territory among boulders and crevices in the shallow-to-intermediate littoral zone, roughly 7–49 ft. Water chemistry follows the Lake Malawi norm: warm, hard and alkaline, typically 75–82 °F and pH 7.7–8.6.
Feeding
As with other Pseudotropheus, this form is presumed to be a specialised aufwuchs grazer, using its rasping dentition to crop the mixed mat of filamentous algae, diatoms and associated micro-invertebrates that coats sunlit rock in the shallows. No feeding study specific to this population exists, but this diet is close to universal across rock-dwelling mbuna in the genus, and Thumbi West Island's exceptionally dense and diverse cichlid community is a well-documented example of fine-grained resource partitioning among co-occurring algae-grazing species.
Mating
Breeding behaviour is presumed to follow the standard mbuna pattern: polygynous and lek-like, with no pair bond. A dominant male holds and defends a patch of rock, often centred on a crevice or small cave, and displays to attract passing females rather than forming an exclusive pairing; subordinate males remain plainer and are largely excluded from the best territory. No behavioural documentation specific to "Tiny" exists, and this account follows the well-established pattern for Pseudotropheus generally rather than direct observation of this population.
Breeding
Pseudotropheus sp. "Tiny" 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; given the trade name's implication of a smaller adult body size, clutches are plausibly smaller than the genus-typical few dozen eggs, but this is inference rather than a measured figure.
In the aquarium
Pseudotropheus sp. "Tiny" should be kept as a standard rock-dwelling mbuna, and if its trade name's implied small adult size holds true, it may suit a somewhat more modest tank than larger Pseudotropheus, though the fundamentals of mbuna care still apply. Dense, stable rockwork built into a tank of at least 47 in gives territorial males room to hold separate ground, with a sand or fine gravel substrate completing the setup. 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 mbuna are poorly suited to high-protein foods, which are strongly implicated in Malawi bloat. Keep a surplus of females per male, and take care with tankmate sizing given a smaller adult body may be more vulnerable to larger, more aggressive mbuna than a typical Pseudotropheus.
Conservation
No IUCN Red List assessment exists for Pseudotropheus sp. "Tiny", and none can while it remains formally undescribed; no status, category or year should be attached to it. Thumbi West Island sits within the protected boundaries of Lake Malawi National Park, which affords its rocky-shore cichlid community more formal protection than most of the lake's shoreline, but that protection does not translate into a species-level assessment for an undescribed, single-locality form like this one. No population-specific study documents its actual abundance or trend, so the accurate statement is that it is unevaluated.