Taxonomy & naming
Melanocharacidium dispilomma was described by the Brazilian ichthyologist Paulo Buckup in 1993 and placed in the genus Melanocharacidium, a group of small darter-characins within the family Crenuchidae — the South American darters — in the order Characiformes. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises the species as valid under this combination, and there is no evidence in the sources reviewed here of a later reclassification; the genus name itself signals the family relationship, combining a reference to dark coloration with the older, broader genus name Characidium, to which many of these small darters were once assigned before being split out.
The species epithet dispilomma describes its most useful field mark: FishBase glosses it as referring to two dark marks above the orbit (the eye), a pattern that helps distinguish it from other small, cryptically coloured Melanocharacidium and Characidium species sharing the same rocky-stream habitats. As with many of the smaller, recently described crenuchids, comprehensive population-level taxonomic review is limited, and this account should be read as reflecting the currently accepted combination rather than an exhaustive systematic history.
Morphology
Melanocharacidium dispilomma is a genuinely small fish — FishBase records a maximum published length of 2 in total length, placing it firmly in nano-fish territory alongside other Crenuchidae such as Elachocharax and the smaller Characidium species. Like other darters in the family, it has an elongate, subcylindrical body built for perching and short bursts of movement along the substrate rather than sustained open-water swimming, with the paired fins positioned to brace against current and rock.
The two dark marks above the eye referenced in its species name are a useful identification feature, and hobbyist accounts note that the species can shift its coloration markedly depending on mood, background and stress level — a trait shared with several small, cryptically patterned crenuchids that rely on camouflage against rocky or leaf-littered stream beds. Detailed published data on sexual size or shape differences is not available in the sources reviewed here.
Habitat
The species is native to northern South America, with FishBase citing records from the Amazon, Orinoco and Essequibo river basins along with coastal stream systems running from Guyana to French Guiana; hobbyist sourcing notes add Bolivia, Brazil, Venezuela and Colombia to its broader range. Within that range it is a benthopelagic fish of upper river reaches and rapidly flowing creeks with rocky or stone substrate — fast, well-oxygenated water rather than the sluggish blackwater pools associated with some other Amazonian nano-characins.
FishBase gives a documented temperature range of roughly 77–84 °F, consistent with lowland tropical streams rather than cooler upland or subtropical water. Specific pH and hardness data were not found in the sources reviewed here; given the rocky, current-swept habitat described, keepers should not assume extreme soft blackwater conditions without further evidence, and should aim to replicate clean, well-oxygenated, moderately warm running water.
Feeding
As a small crenuchid darter, Melanocharacidium dispilomma is a micro-predator rather than an omnivorous grazer or scavenger. FishBase records a mid-range trophic level (3.3 ± 0.3), consistent with a diet of small aquatic invertebrates — insect larvae, micro-crustaceans and similar prey picked from the rocky substrate and current — rather than significant plant or detrital material.
Aquarium sourcing describes the species as harmless toward tankmates and plants, reinforcing that it is not a fin-nipper or a threat to vegetation; it forages by darting and perching rather than by cruising and grazing. In the aquarium, keepers of similarly sized crenuchid darters typically find that these fish often ignore dried flake and prefer small live or frozen foods such as microworm, baby brine shrimp or cyclops — specific feeding notes for this exact species were not found in the sources reviewed here, so this guidance follows from its documented micro-predator biology and family behaviour rather than a direct source.
Mating
No courtship or spawning description specific to Melanocharacidium dispilomma was found in the sources reviewed here. Within Crenuchidae more broadly, the best-studied genera — Crenuchus and Poecilocharax — are cave or leaf-site spawners in which a male attracts a female to a chosen surface and briefly tends the resulting clutch, while species in the related genus Characidium are generally understood to scatter eggs over the substrate without forming a defended nest site. Given that Melanocharacidium sits taxonomically between these groups within the family, either pattern is plausible, but this account does not assign a specific courtship description to this species without direct evidence.
Breeding
Breeding data specific to Melanocharacidium dispilomma is sparse in the sources reviewed here, and no aquarium spawning reports were found. Based on what is documented for its family, Crenuchidae breeding is not uniform: the sailfin characins Crenuchus spilurus and Poecilocharax are cave/leaf spawners with brief male care of a small clutch, a pattern that has made them genuinely breedable at nano scale in specialist aquaria, while stream-bed Characidium species are understood to be substrate egg-scatterers with no sustained parental care.
Without a confirmed source for this particular species, this account cannot state definitively which pattern M. dispilomma follows, or whether it has been bred in captivity at all — readers should treat any claim of routine home breeding for this species as undocumented rather than assume egg-scattering or male care by default.
In the aquarium
Melanocharacidium dispilomma is a true nano fish at a maximum of 2 in, well suited in principle to smaller, well-filtered aquaria rather than the large tanks needed for its serrasalmid relatives elsewhere in this family group. Aquarium trade sourcing describes it as completely harmless toward tankmates and plants and suitable for keeping with conspecifics, consistent with its documented role as a small, non-aggressive substrate micro-predator; its low FishBase fishing-vulnerability score (10/100) further reflects a hardy, resilient small stream fish rather than a fragile specialist.
Given its native habitat of rapidly flowing, rocky, well-oxygenated creeks at 77–84 °F, a tank replicating flowing water over stone and gravel with good water quality is a reasonable starting point, though keepers should note that detailed aquarium husbandry accounts for this exact species are limited compared with better-known nano crenuchids, and specific stocking, filtration and diet recommendations here are inferred from its documented biology rather than confirmed aquarium-keeping literature.
Conservation
Melanocharacidium dispilomma is assessed by the IUCN Red List as Least Concern, an assessment consistent with a wide distribution across the Amazon, Orinoco and Essequibo basins and Guianan coastal streams, and with no specific threats documented in the sources reviewed here. Its low fishing-vulnerability score on FishBase further suggests a resilient, widespread small stream fish rather than a narrow-range or heavily pressured species.
As with many small, non-commercial characins, detailed population trend data is not available, and the Least Concern status should be read as reflecting broad range and apparent abundance rather than close monitoring. General pressures on Amazonian, Orinoco and Guianan headwater and rocky-stream habitats — deforestation, mining-related sedimentation and water-quality change — are relevant long-term watch items for this habitat type even though the species itself is not currently classified as threatened.