Taxonomy & naming
The species was described in 1968 by the Belgian ichthyologist Dirk Frans Elisabeth Thys van den Audenaerde, in the Revue de Zoologie et de Botanique Africaines, as Pelmatochromis roloffi — figured in the same work in which he erected the subgenus Pelvicachromis for the dichromatic dwarf 'kribs'. The type series came from Kwako Lake in the old Sherbro District of southern Sierra Leone; the holotype (MRAC 73399) and three paratypes are held at the Royal Museum for Central Africa in Tervuren. As Pelvicachromis was raised to full genus rank the fish became Pelvicachromis roloffi, and that combination has been carried through every subsequent treatment — the CLOFFA check-list (Daget 1991), the Faune des poissons d'eaux douces et saumâtres de l'Afrique de l'Ouest (Lévêque, Paugy & Teugels), and Anton Lamboj's revisionary work on the genus (2001, 2004, 2013). Eschmeyer's Catalog of Fishes lists the current valid name as Pelvicachromis roloffi (Thys van den Audenaerde 1968). It is worth stressing the point, because the genus has lately been split: in 2016 Lamboj, Trummer and Metscher removed the large, elongate 'Type 1' kribs — humilis, rubrolabiatus and signatus — into a new genus, Wallaceochromis. Pelvicachromis roloffi was not among them. It belongs to the smaller, deeper-bodied core of Pelvicachromis alongside Pelvicachromis pulcher, Pelvicachromis taeniatus and Pelvicachromis subocellatus, and remains a Pelvicachromis. The genus sits in the African cichlid subfamily Pseudocrenilabrinae, in the chromidotilapiine group of riverine dwarf cichlids.
Morphology
Pelvicachromis roloffi is a small, slender krib. FishBase gives a maximum of about 3 in total length, and aquarium accounts agree that males rarely exceed roughly 3.5 in while females stay smaller, around 2.5–3 in. The body is moderately deep — body depth runs about 37 to 40 percent of standard length — and more elongate than the rounder pulcher. Fin counts run to 16 or 17 dorsal spines with 9 soft rays, three anal spines and seven soft rays. Two pigment features help separate it from its congeners: the dorsal fin carries a row of several dark spots, of which the last three are conspicuously larger and darker than the rest, and there is a distinct black spot at the base of the caudal fin. As in all kribs the sexes differ sharply and, unusually, the female is the showier of the two. Males are the larger, longer-finned and plainer sex, grey-brown to olive along the back with a dark mid-lateral stripe and lyre-shaped or lengthened outer caudal rays in old fish. Spawning females shrink and round their bodies, the belly blazing a deep wine-red to violet, the dorsal fin lifting into a banner edged in red with a pale bluish submargin — a diagnostic detail that Lamboj used to separate roloffi females from those of the otherwise similar pulcher and sacrimontis. Several geographic colour forms exist across the range, differing in the intensity of the female's red and the exact dorsal-fin pattern.
Habitat
The species is endemic to the Upper Guinea region of West Africa. FishBase summarises its range as the River Kolenté (the Great Scarcies) in Guinea, south through Sierra Leone to western Liberia, and the IUCN assessment treats it as a wide-ranging coastal-river fish of those three countries. The georeferenced museum material bears this out: collections sit on the Kolenté near Kindia and around Rokupr, on the Waanje and Taja rivers and their marigots in southern Sierra Leone, at Kwako Lake in the Sherbro district (the type locality), and in swamps and creeks east of Mano in Liberia. This places it across the Northern and Southern Upper Guinea freshwater ecoregions — short coastal rivers descending from the Guinean highlands, noted for high fish endemism. Its biotope is the small forest stream and its associated swamps: it is found 'primarily in smaller rivers and creeks, although it may also be found in shallow waters near the banks of larger rivers', typically among leaf litter, roots and marginal vegetation. The water is soft, warm and acidic to neutral. FishBase records a pH window of about 5.9 to 7.0, a strikingly low hardness of only 1 to 2 dH, and a temperature range of 75–79 °F — the soft, dark, mineral-poor blackwater of the West African forest floor. These are shallow-water fish of the upper metre or so of small, shaded streams rather than of deep open channels.
Feeding
Pelvicachromis roloffi is a benthic micro-omnivore that works the stream bed and leaf litter of its forest habitat. FishBase estimates a trophic level near 3.3, in line with a diet that mixes small invertebrates with algal and detrital material. In the wild it takes aquatic insect larvae, micro-crustaceans and other small invertebrates picked from the substrate, along with aufwuchs — the film of algae and detritus grazed from submerged wood, leaves and stones. No dedicated wild gut-content study has been published for the species, so this picture is inferred from its close relatives and from its mouth and body form rather than measured directly. In the aquarium it is an unfussy if cautious feeder, taking small live and frozen foods — cyclops, daphnia, brine shrimp, grindal and microworm — readily once settled, and accepting good-quality crushed flake and micro-pellet, though it does best when those staples are balanced with a vegetable component, as with the genus generally. As a small, bottom-oriented forager in low-productivity forest streams it occupies the generalist invertivore-detritivore niche typical of the krib lineage rather than any specialised feeding role.
Mating
Like all kribs, Pelvicachromis roloffi forms a monogamous pair bond and reverses the usual cichlid roles, with the female taking the active part in courtship. When she ripens, her belly flushes deep red and her body shortens and deepens; she seeks out the male and displays to him side-on, arching her body into a curved, shimmying posture that shows off the red belly and the raised, banner-like dorsal fin, and she presses this display until the larger, plainer male responds. The pair then choose and prepare a spawning cave together — a crevice among roots or stones, an excavated chamber under wood, or in aquaria a flowerpot or coconut shell — testing and cleaning the site before committing to it. The species is described as shy and easily intimidated, slower to settle and to spawn than the common krib, so in the aquarium pairs are best allowed to form on their own from a group of young grown on together, rather than arbitrarily matched. As is usual in the genus, both fish guard the territory once a site is chosen, but the female dominates the immediate vicinity of the cave.
Breeding
Pelvicachromis roloffi is a biparental cave spawner. The female lays her adhesive eggs on the roof or wall of the chosen cave and then tends and fans the clutch, while the male patrols and defends the surrounding territory — a division of labour shared across the genus. Detailed published clutch counts are scarce for this species; in the krib genus, cave clutches typically run from a few dozen to perhaps one hundred or more eggs, and roloffi, as one of the smaller members, sits at the lower end of that band. By analogy with its close relatives the eggs hatch in roughly three days, and the larvae become free-swimming and leave the cave about a week to ten days after spawning, the parents shepherding the school of fry through the leaf litter and relocating them among freshly dug pits. Both parents guard the brood for several weeks. The fry are small and are reared on the usual first foods — newly hatched brine shrimp, microworm and finely powdered flake — and respond, like the adults, to clean, soft, warm water with frequent partial changes. Hobby reports note that, as with other kribs, soft and acidic water can bias the brood's sex ratio, and that the species can be a tentative and inconsistent breeder until it is thoroughly settled and the pair securely bonded.
In the aquarium
Roloff's krib is a rewarding but slightly demanding dwarf cichlid, and not the most forgiving krib for a beginner — its shyness and its taste for very soft water set it apart from the bombproof common krib. A single pair is comfortable in a modest tank of around 23.5–31.5 in length, but the aquascape matters more than the volume: it should be densely structured with driftwood, roots, rockwork and several caves or upturned flowerpots, with planting and leaf litter to break sightlines and give the easily intimidated fish places to retreat. A dark, fine substrate, subdued lighting and tannin-stained water bring out both its colour and its confidence. Water should mirror the soft forest streams it comes from — a temperature around 75–81 °F and a pH on the acidic side of neutral, kept genuinely soft (the wild hardness is only 1 to 2 dH), with breeding best attempted softer and more acidic still. It is a peaceable fish toward other species and is easily bullied, so tankmates should be small and calm: upper-water dither fish such as small West African tetras or Ladigesia, plus the African butterfly cichlid Anomalochromis thomasi, suit it well, while boisterous or much larger fish will keep it permanently hidden. Toward its own kind it is territorial in the usual krib way, so keep a single compatible pair unless the tank is large and heavily broken up. It remains uncommon in the trade — collected occasionally from West Africa and bred by specialists rather than mass-produced — and rewards the patience of a keeper who can give it the quiet, soft-water blackwater setup it wants.
Conservation
The IUCN Red List assesses Pelvicachromis roloffi as Least Concern, in an assessment dated 9 November 2019 for the pan-African freshwater fish review. The species is relatively widespread across the coastal river basins of Guinea, Sierra Leone and Liberia, is not known to face a population-level threat, and carries no CITES listing. That said, the Upper Guinean forest-stream ecosystems it depends on are under steady and growing pressure: deforestation and the clearing of catchment forest, agricultural expansion, alluvial and gold mining with the siltation that follows, and the general degradation of the small, shaded streams and swamps that constitute its habitat. The region holds a highly endemic freshwater fauna in some of the most reduced forests in West Africa, so while the species itself is currently judged secure, its long-term prospects are tied to the fate of those forest watersheds. As with several kribs, the existence of distinct regional colour forms is also a quiet reminder that individual local populations may be more restricted — and more vulnerable to a single catastrophe — than the broad species range suggests.