Taxonomy & naming
George Albert Boulenger described the species in 1915 as Paratilapia thomasi, working from a small series of West African cichlids that the British anthropologist Northcote Whitridge Thomas gathered during his ethnographic survey of Sierra Leone. Eschmeyer's Catalog of Fishes fixes the type locality as Maka, Sierra Leone, and records a lectotype (BMNH 1914.12.9.9) with two paralectotypes in the Natural History Museum, London; P. H. Greenwood designated that lectotype in 1985. For decades the fish was passed from one West African cichlid genus to another, appearing in the older literature as Haplochromis thomasi, Hemichromis thomasi and Pelmatochromis thomasi — none a good fit, since it shares neither the haplochromine mouthbrooding habit nor the dentition of those groups.
Greenwood settled the matter in 1985 by erecting the monotypic genus Anomalochromis, the name marking an 'anomalous' chromid that would not sit in any existing pigeonhole. Both the Catalog of Fishes and FishBase treat Anomalochromis as valid and Anomalochromis thomasi (Boulenger, 1915) as its only species, the parentheses on the authority recording Boulenger's original placement in a different genus. Because it remains the sole member of the genus, Anomalochromis and the fish are effectively one and the same. Its closest relatives are the small West African 'pelmatochromine' cichlids — the kribs and their kin — rather than the jewel cichlids it can resemble in a shop tank.
Morphology
Anomalochromis thomasi is a genuine dwarf. FishBase gives a maximum of 2 in standard length, the largest recorded fish about 2.5 in total length, and most aquarium adults fall between 5 and 3 in overall — a deep, laterally compressed body built like a small butterfly. The fins carry 14–15 dorsal spines with 8–10 soft rays and 3 anal spines with 7–9 soft rays, the spinous dorsal typical of the substrate-spawning African cichlids.
Colour is what earns the common name. Juveniles and unsettled fish are a plain greenish-grey with a broken lateral stripe and a few dark blotches, but a settled adult warms to an amber or coppery-bronze ground scattered with rows of sky-blue to blue-green spangles across the flanks, gill covers and unpaired fins, crossed by darker vertical bars the fish can switch on and off with its mood. A dark mid-lateral blotch and a spot at the tail base show through most colour states. Dimorphism is real but subtle: males run slightly larger with more produced, pointed tips to the dorsal and anal fins, while ripe females are rounder-bellied and — unusually for a cichlid — often the brighter of the pair. Outside of breeding, telling the sexes apart with confidence is hard.
Habitat
The African butterfly cichlid is endemic to the coastal rivers of the Upper Guinean forest belt in westernmost Africa. FishBase summarises the range as the coastal drainages from the Konkouré in Guinea south to the St. John in Liberia, taking in much of Sierra Leone between — the same band of short, forest-fed rivers that produces Pelvicachromis roloffi, Pelvicachromis humilis and the true Hemichromis bimaculatus. These are the Northern and Southern Upper Guinea freshwater ecoregions, coastal systems draining the Guinean highlands and noted for their high fish endemism.
Within that range the fish keeps to small rivers, streams and quiet backwaters, in both shaded forest reaches and more open, savannah-bordering waters. The water is soft and warm, often tannin-stained, and the fish hold to the lower and middle layers among leaf litter, roots, driftwood and dense marginal plants. FishBase records a pH window of roughly 6.0–8.0, a hardness of about 5–12 dH and a temperature band near 73–81 °F, with tolerance of warmer water approaching 86 °F; the soft, slightly acidic, tannin-rich end of that range best matches the forest-stream biotope. One field note recurs in the literature: when alarmed, the fish dives into soft mud and buries itself — to as much as 12 in down — a defence unusual among cichlids and well suited to the shallow, muddy margins it favours.
Feeding
Anomalochromis thomasi is a small generalist forager. It takes mostly animal prey but readily accepts plant and detrital matter, and FishBase places it at a modest trophic level of about 3.2 — a micro-predator of the streambed, not a piscivore. In the wild it works the bottom and the structure for aquatic insect larvae, small crustaceans, worms and other invertebrates picked from the leaf litter, rounding the diet out with algae and incidental vegetable matter.
At the dinner table it is famously undemanding. Good-quality flake and small pellets go down without fuss, and live or frozen items — bloodworm, brine shrimp, daphnia, cyclops and the like — bring up its colour and condition it to spawn. A varied, slightly carnivore-leaning diet with regular live or frozen feeds suits it best, but its willingness to eat almost anything offered is part of what makes it such a forgiving first cichlid.
Mating
Like its larger pelmatochromine and jewel-cichlid relatives, Anomalochromis thomasi is monogamous and biparental, and the pair bond is the centre of its breeding life. The usual route is to raise a small group and let fish pair off naturally; a settled pair then claims and defends a territory around a chosen spawning surface. Courtship runs on colour — both partners deepen to their amber-and-blue breeding dress and display flank to flank, with quivering, fin-spreading and the gentle jaw-sparring typical of substrate-spawning cichlids.
What sets this fish apart from its kin is how mild the whole business stays. Outside spawning it is genuinely peaceful, and even a breeding pair is only modestly territorial by cichlid standards, defending a small zone around the brood rather than commandeering the tank. Pairs are stable, and the mate aggression that makes jewel cichlids and many other open-spawners hazardous is largely absent — the main reason the species is so often recommended for a keeper's first cichlid spawn.
Breeding
Anomalochromis thomasi is a textbook biparental open-substrate spawner. The pair chooses and thoroughly cleans a firm surface — a flat or gently sloping rock, a broad leaf, a piece of driftwood or a cleared patch of substrate — and the female lays rows of adhesive eggs across it while the male follows to fertilise each batch. The spawns are large for so small a fish: a few hundred eggs is common, and exceptional clutches of up to around 500 are reported.
Both parents then mount an intensive shared watch. They fan and guard the eggs, pick out whitened infertile ones, and on hatching move the wriggling larvae to one or more shallow pits, shuttling them between. Within a few days the fry are free-swimming and led about the territory as a tight cloud, both parents herding strays back in. The species breeds readily in well-kept soft, warm water, and the fry take newly hatched brine shrimp nauplii and finely powdered dry foods from the start. Small size, easy spawning and gentle, dependable parenting have made Anomalochromis thomasi a favourite first project for aquarists learning to breed cichlids.
In the aquarium
Widely rated one of the best beginner cichlids and a genuinely good community fish — a rare combination in the family. It is small, hardy, undemanding about food, peaceable outside of breeding and, in adult dress, beautiful.
Tank: a pair is comfortable from about 31.5 in of length. The setup that suits it is a soft, dimly lit forest-stream biotope — a dark substrate to deepen the fish's colour, driftwood, smooth pebbles and flat stones for spawning, and generous planting (including floating plants to cut the light) with open swimming space at the front.
Water: chemistry is easy — a pH around 6.0–7.5, soft to moderately soft water (roughly 5–12 dH) and a temperature in the mid-to-high 20s °C (about 75–82 °F), with the softer, more acidic, tannin-stained end of that range encouraging breeding.
Tankmates: its temperament fits a wide range of small, peaceful fish — upper-water schoolers such as small tetras or rasboras, and other gentle dwarf cichlids including Pelvicachromis species in a large enough tank. As with any cichlid, a pair guarding eggs or fry turns more defensive of its small patch and should be given room.
Feeding is straightforward, the fish taking dry, frozen and live foods with equal appetite. For anyone who wants the parenting drama and colour of a cichlid without the aggression and bulk, Anomalochromis thomasi is hard to beat.
Conservation
The IUCN Red List assesses Anomalochromis thomasi as Least Concern, in an assessment dated 2019. Small, adaptable and fecund, and spread across the coastal rivers of three West African countries, it faces no species-level threat at present; it is of no fisheries interest, harmless to people, and not listed by CITES.
The wider context is the state of its habitat. The Upper Guinean forest streams of Guinea, Sierra Leone and Liberia are among the more heavily pressured freshwater landscapes in Africa, where deforestation, alluvial and artisanal mining, siltation and pollution are degrading the small clear and tannin-stained waters the fish depends on. None of this is currently flagged as a specific danger to Anomalochromis thomasi, and its tolerance of a wide range of conditions — including the muddy, savannah-bordering reaches it can retreat into — lends some resilience. But the species' long-term health is tied to the same forested coastal drainages that shelter the region's other endemic cichlids.