Taxonomy & naming
Protomelas sp. "Spilonotus Tanzania" has no formal scientific description, no describing author, and no year of publication. When live specimens first reached German aquarists in October 1992, collected from the northeastern, Tanzanian side of Lake Malawi, they were initially labelled Protomelas insignis — a misidentification that was later corrected. The trade name that replaced it, "Spilonotus Tanzania," signals what the fish actually is understood to be: a population closely related to the described species Protomelas spilonotus, distinguished from it by locality and by details of male colour rather than by any formally published anatomical character. Lake Malawi is the name most aquarists know the lake by, but Tanzanian and Mozambican fishers still use its older name, Lake Nyasa, which turns up throughout the older literature on this fish. Until a taxonomic revision formally addresses the spilonotus complex, this population should be treated strictly as an undescribed, informally recognised form.
Morphology
This is a moderately large, laterally compressed Protomelas on the genus's typical elongate plan. Males reach roughly 8 in and are noticeably larger than females, which grow to about 6 in. Breeding males carry a brilliant, saturated blue over the head and body, set off by a broad white marginal band along the dorsal fin; the lower third of the body and the lower part of the caudal peduncle are a deep yellow-orange, giving the fish a striking two-tone blue-and-orange effect that is the main reason it is prized in the hobby. Females and non-territorial males are far plainer: a grey-brown ground colour carrying a pattern of three horizontal spot-rows, the classic haplochromine female livery. The uppermost row sits just below the dorsal fin base and shows only four or five distinguishable spots; a second, shorter row of three or four spots lies just above the lateral line; the most conspicuous row runs midlaterally, starting about a centimetre behind the gill cover and continuing to the caudal peduncle, appearing as a broken line of elongated spots because it is interrupted two or three times. The number and shape of these spots vary between individuals within a population.
Habitat
This form is documented along the northeastern, Tanzanian shoreline of Lake Malawi, where steep rocky coasts and large boulders form sizeable caves and crevices. Rather than hugging the rock face, these cichlids favour the upper few metres of open water directly above and among large rocks — an intermediate habitat between pure rock-dwelling and open-water living. Divers report the species is genuinely scarce below about 6 metres and becomes rare with increasing depth; fish taken from greater depths need to be decompressed gradually before being brought to the surface, unlike specimens caught in the shallow top layer. The fish is shy and keeps a large flight distance from divers, retreating into rock crevices when approached too closely. As with the rest of Lake Malawi's water column, conditions here are warm, hard, and strongly alkaline.
Feeding
Protomelas sp. "Spilonotus Tanzania" feeds on invertebrates picked from the open water column rather than grazed off rock surfaces, a habit tied closely to its preference for steep, wave-exposed rocky coasts. Such coasts are well exposed to wind and wave action, and the resulting turbulence stirs up food-rich sediment that is then suspended in the water column and made available to fish feeding in this way. Large foraging groups made up of females and males showing only faint traces of their normal breeding colour wander through the habitat and appear to be attracted specifically to areas of freshly stirred-up sediment, picking small invertebrates out of suspension as they go.
Mating
Breeding males are territorial and occupy sites in the upper part of the rocky biotope, in the water column above and around large boulders rather than on open sand. As in other Lake Malawi haplochromines the system is polygynous: males display and defend a spawning site rather than pairing, and females move through the habitat to visit colour-holding males. Because breeding males hold their bright blue-and-orange colour more or less continuously in this species, males can be spotted from the surface even without diving, though the same conspicuousness makes them wary of divers who approach too closely.
Breeding
Spawning occurs directly in the rocky habitat, either inside caves and crevices among the boulders or on the open surface of the rocks themselves — a departure from the sand-pit spawning typical of many open-water Malawi cichlids. As a maternal mouthbrooder, the female takes the fertilised eggs into her mouth immediately after spawning and carries the developing brood there for several weeks, foregoing normal feeding for most of that period before releasing free-swimming fry. There is no male or biparental care beyond fertilisation. Clutch size and exact brooding duration have not been documented specifically for this population.
In the aquarium
"Spilonotus Tanzania" has been established in the hobby since the early 1990s and is kept for the vivid blue-and-orange colour of dominant males. Because wild-caught individuals were historically collected from depths that required staged decompression, captive-bred stock is both more available and less stressful to acclimatise; buyers should confirm provenance where a pure locality line matters.
A generous rock structure with caves and open swimming space in the upper part of the tank suits its natural habit of foraging in mid-water above boulders rather than tight against the rock face. A tank of at least 59 in in length gives a male room to hold a colour territory without constant harassment of females and subordinate males. Water should match Lake Malawi conditions closely — warm, hard, and alkaline, with a stable pH clearly on the alkaline side of neutral — since this genus is intolerant of soft or acidic conditions over the long term.
Because males hold nuptial colour for extended periods and are drawn to any similarly coloured rival, keeping one male with several females reduces aggression compared with multiple-male groups in modest tanks. Diet should mimic its natural habit of picking invertebrates from open water: a quality pellet supplemented with frozen or live zooplankton-type foods such as daphnia and brine shrimp, rather than a diet centred on algae or vegetable matter.
Conservation
Protomelas sp. "Spilonotus Tanzania" has no IUCN Red List assessment, because it has never been formally described and therefore has no valid scientific name to assess. This is a statement about taxonomic status, not about population health. As a shy, locality-restricted rock-and-open-water cichlid along the Tanzanian coast, it faces the same general pressures common to Lake Malawi's ornamental cichlids — collection pressure at known export sites and the broader effects of shoreline disturbance — but no specific population data or formal conservation status exists to characterise its actual risk.