Taxonomy & naming
Distichodus decemmaculatus was described by the French ichthyologist Jacques Pellegrin in 1926, one of dozens of Congo basin fish species he named during his long career cataloguing Central African freshwater fauna. It belongs to the family Distichodontidae within the order Characiformes, a family of African herbivorous and omnivorous characins whose members range from this species' nano scale up to the metre-plus Citharinus food fishes.
The genus Distichodus is recognised by the Catalog of Fishes (Eschmeyer, California Academy of Sciences) as the valid combination for this species; there is no old-combination confusion to note here, unlike the heavy genus-splitting seen in the South American Serrasalmidae. The specific epithet decemmaculatus is straightforward Latin — "ten-spotted" — describing the row of dark markings along the lateral line that gives the species its common trade name, dwarf distichodus.
Morphology
Like all Distichodus, this species has an elongated, laterally compressed body and a small, underslung mouth set for grazing rather than biting, with the family's characteristic overlapping, herringbone-patterned scale rows along the flank. FishBase and hobby sources agree on a small adult size of roughly 2–3 in total length, with 3 in cited as the maximum — a fraction of the 15.5–35.5 in reached by large congeners such as D. sexfasciatus.
The defining field mark is a series of 7–12 round, dark spots strung along the lateral line, set against a silvery-olive body that can take on a warm brassy sheen under good light. Fins are unremarkable and translucent to pale amber, without the bold red or black fin markings seen in some other Distichodus. No reliable external difference between sexes has been documented for this species.
Habitat
Distichodus decemmaculatus is endemic to the Central Congo basin, where it is found along grassy, vegetated margins of large and medium rivers in slow-to-moderate current. It is a pelagic, schooling species, moving in loose shoals through marginal cover rather than holding station in open water.
Water in its native habitat is slightly acidic and warm: FishBase gives a temperature range of roughly 73–81 °F (optimum near 77 °F) and pH 6.5–7.5, figures echoed by hobby sources citing 73–81 °F at the same pH band. These are moderate, soft-to-neutral Congo basin conditions rather than the extreme blackwater chemistry associated with some other Central African biotopes.
Feeding
This species is a phytophagous-leaning omnivore: FishBase describes its natural diet as dominated by vegetation, supplemented with worms and other bottom invertebrates, and hobby sources are consistent in flagging it as a dedicated plant-shredder despite its small size. It grazes continuously over soft plant matter and biofilm rather than hunting.
In the aquarium this translates directly into feeding practice: offer vegetable-forward foods — blanched vegetables, spirulina-based flake or pellet, algae wafers — alongside occasional small live or frozen protein such as bloodworm or daphnia to round out the diet. Keepers should expect any soft-leaved live plants in the tank to be treated as food rather than décor.
Mating
No aquarium-documented courtship behaviour is captured in available sources for this species. FishBase records it as oviparous, with females producing on the order of 1,000–1,550 small yellow eggs around 0.5 in in diameter, consistent with an egg-scattering reproductive strategy typical of the genus, but no description of pairing, courtship display or spawning triggers has been established.
External sexual dimorphism is not documented for this species; there is no known reliable way to visually sex individuals outside of examining gravid females for a fuller body during spawning condition, and even that is not confirmed in the sources available.
Breeding
Distichodus decemmaculatus is, like the rest of its genus and the related citharinids, an egg-scattering species that is not regularly bred in the aquarium — FishBase explicitly notes it is not commonly reproduced in captivity. This matches the broader pattern across African Distichodontidae, where successful home breeding is rare and undocumented in detail even though fecundity in the wild (over a thousand eggs per spawn) is substantial.
Prospective breeders should treat this as an open question rather than a solved protocol: there is no established aquarium spawning method to report, and keepers attempting it would be working largely from first principles (soft, slightly acidic water and a mature, well-fed shoal) rather than a documented playbook. Most specimens in the trade are wild-collected or farmed abroad rather than hobbyist-bred.
In the aquarium
Despite belonging to a genus with some genuinely large, tank-dominating species, Distichodus decemmaculatus stays small — under 3 in — which makes it one of the few Distichodus genuinely suited to modest aquaria. Hobby sources recommend a minimum of roughly 15 US gal for a single fish, scaling up to 200+ litres for a proper shoal, since this is a schooling species that does best in numbers rather than alone.
The major care caveat is the same one that applies across the genus at any size: this fish is not compatible with live plants. Its herbivorous grazing will strip soft-leaved species down to bare stems, so aquascape with hardy, tough-leaved plants (Anubias, Java fern) or hardscape and artificial planting instead. Keep water warm (roughly 73–81 °F) and mildly acidic to neutral (pH 6.5–7.5), and maintain a real group to reduce stress and support natural shoaling behaviour.
Conservation
The IUCN Red List assessed Distichodus decemmaculatus as Least Concern in 2009, reflecting its wide distribution and lack of major documented threats across the Central Congo basin. It is not a species of conservation concern.
As a Central African endemic tied to a specific basin, the species shares the longer-term watch items facing Congo basin freshwater fish generally — habitat pressure from deforestation, water-quality change and regional development — even though no current threat has elevated its status above Least Concern. The aquarium trade in this species appears to rely at least partly on wild collection, though export volumes and any farming activity are not detailed in available sources.