Taxonomy & naming
Distichodus teugelsi was described in 2008 by Victor Mamonekene and Jos Vreven, part of a wave of Congo-basin distichodontid revisions in the early 2000s that split out several small-bodied species previously lumped with better-known Distichodus. It belongs to the family Distichodontidae — the African citharinoid characins — within the order Characiformes, a family the Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats as distinct from the South American Serrasalmidae despite superficial resemblance in some species.
The genus Distichodus spans a huge range of adult sizes, from nano species like this one to the 60-cm-plus D. sexfasciatus and D. lusosso kept by predator-tank enthusiasts, and the trade name "green dwarf distichodus" specifically distinguishes D. teugelsi from those much larger, more aggressive relatives. Reliable identification within the small-bodied Congo Distichodus rests on fin markings, body proportions and locality, and the species is still relatively obscure outside specialist Congo-fish circles.
Morphology
Distichodus teugelsi has the elongate, moderately compressed body typical of the genus, with a small, terminal, protrusible mouth adapted for grazing rather than the more oblique jaw of predatory characins. FishBase records a maximum size of 2 in standard length (roughly 2.5 in total length), making it one of the smallest described species in Distichodus — a genus otherwise dominated by fish several times that length.
Colouration is a soft olive-to-green ground shade along the flanks, giving rise to the common name, typically with the fine vertical banding and delicate finnage seen in miniature distichodontids. Aquarium Glaser notes a degree of sexual dimorphism: males run smaller than females, and females develop a noticeably fuller belly, a useful field mark for anyone trying to sex a group.
Habitat
Distichodus teugelsi is native to the Democratic Republic of the Congo, recorded from the middle course of the Congo River. Like many Congo-basin fish it inhabits flowing river habitat rather than still water, and the Aquadiction care guide describes it as an active swimmer that does best with a strong current mimicking its riverine origin.
Congo River water in this stretch is generally soft to moderately mineralised and can run acidic depending on season and tributary influence. Aquarists replicating this species' habitat should lean toward soft, current-rich setups rather than the still, heavily planted tanks associated with some other characins — a preference borne out by the fish's own foraging behaviour, described below.
Feeding
All Distichodus species require a meaningful proportion of plant matter in the diet, and D. teugelsi is no exception, but at this small size its feeding style is closer to grazing omnivore than the destructive vegetarian behaviour of its giant relatives. FishBase and the Aquadiction care guide both describe it as omnivorous, taking detritus, algae, soft plant material and small invertebrates or crustaceans encountered while foraging over current-swept substrate.
In the aquarium it will browse soft-leaved or delicate plants but is reported to leave tougher, more robust species such as Anubias, Bolbitis and Java fern largely alone — a useful distinction from larger Distichodus, which shred almost anything green. A diet built around algae wafers, blanched vegetables, spirulina-based foods and occasional live or frozen invertebrates suits the species' grazing habits well.
Mating
No courtship behaviour has been documented for Distichodus teugelsi in the sources reviewed here. Aquarium Glaser notes that conspecifics engage in minor, non-serious territorial disputes, which in other small Distichodus species can be a precursor to pairing behaviour, but no confirmed spawning account, courtship display or pair-formation sequence has been published for this species. This is consistent with the genus and family generally: most Distichodus and citharinid characins are egg-scatterers whose reproductive behaviour in the wild and in captivity is poorly studied.
Breeding
Distichodus teugelsi has not been reported bred in the aquarium, and no spawning mode has been documented specifically for this species in the available literature. As an African characin in the Distichodontidae, it almost certainly follows the family's general pattern of egg-scattering with no parental care, but this should be read as an inference from its relatives rather than a confirmed observation — Distichodus as a genus is notoriously difficult to breed in captivity, and hobby accounts of home spawns are essentially absent.
Prospective keepers should treat this species as effectively wild-collected or commercially propagated stock rather than something they can expect to breed at home; anyone who does succeed would be documenting new ground for the species.
In the aquarium
At under 2.5 in, Distichodus teugelsi is an unusually manageable member of a genus that otherwise demands very large tanks, and this is its main selling point: keepers get authentic Congo-river Distichodus character without the eventual 15.5–27.5 in predator-tank commitment of D. sexfasciatus or D. lusosso. The Aquadiction care guide recommends keeping it in groups of five or more, reflecting both its social, active-shoaling nature and the genus-wide tendency toward skittishness or stress when kept alone or in poor conditions.
Provide a tank with strong water movement, open swimming space and a mix of tougher plants (Anubias, Bolbitis, Java fern) that will survive its grazing alongside softer growth it can browse. Water should be kept soft to moderate and on the acidic-to-neutral side, matching its Congo River origin; given its small size and peaceful nature, it makes a genuinely community-friendly nano-to-medium characin, in sharp contrast to the reputation of larger Distichodus. As with most obscure Congo endemics, stock is likely to be wild-collected, so buyers should ask retailers about sourcing.
Conservation
The IUCN Red List does not have an easily located species-specific assessment for Distichodus teugelsi in the sources reviewed here; secondary sources describe it as apparently stable within its Congo River range, consistent with a Least Concern-type status, but this should be treated as provisional rather than a confirmed, dated IUCN assessment. General future threats cited for small Congo-basin distichodontids include habitat degradation, pollution and overfishing, though no species-specific population data or trend has been documented.
As with many recently described, narrow-range Congo endemics, D. teugelsi's conservation picture is limited by how little targeted research exists — a data gap rather than evidence of decline, but one worth flagging honestly rather than papering over with an invented assessment.