Pseudotropheus demasoni is one of the smallest mbuna species from Lake Malawi, yet it compensates for its diminutive size with extraordinary aggression. Endemic to Pombo Rocks in northern Lake Malawi, both sexes display nearly identical deep blue and black striped patterns, making sex identification difficult without close examination. Males are extremely territorial and will relentlessly harass conspecifics and similarly colored species, often to the point of killing weaker individuals. Counterintuitively, the recommended strategy for keeping Demasoni is to overstock — maintaining 12 or more individuals spreads aggression and prevents any single fish from being targeted excessively. In the wild, Demasoni graze on aufwuchs — algae and associated organisms on rock surfaces — and the aquarium diet should reflect this herbivorous tendency. Providing a protein-rich diet can contribute to bloat, a common and potentially fatal disease in mbuna. Like all Pseudotropheus, Demasoni is a maternal mouthbrooder, with small clutches of 5–15 eggs incubated by the female. Fry are relatively easy to raise once released. This species is unsuitable for a standard community aquarium but is an excellent and rewarding subject for a species-specific or mbuna-only display.
