Taxonomy & naming
Parodon magdalenensis was described in 2011 by Londoño-Burbano, Román-Valencia and Taphorn, part of a wave of taxonomic work that clarified the diversity of Parodon in Colombia's rivers. It sits in the family Parodontidae — the "scrapetooths" — within the order Characiformes, a family that is often lumped in the public imagination with piranhas and pacus (Serrasalmidae) simply because both are Neotropical characins, but the two families are ecologically and morphologically worlds apart: Parodontidae are small, streamlined, algae-grazing riffle fish, not predators or bulk grazers of fruit and seeds. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) lists Parodon magdalenensis as the currently valid name, with its type locality in the río La Miel, Norcasia, in Colombia's Caldas department, at roughly 2362 ft elevation.
The species epithet magdalenensis refers directly to the Magdalena River system, the major Colombian drainage in which the type locality sits. As with much of the genus, identification of Parodon species rests on fine details of tooth counts, fin-ray formulae and body proportions, and species-level taxonomy within Colombian Parodon has been actively revised in the twenty-first century — so older literature or trade labels referencing this fish may use a different or more generic "Parodon sp." designation.
Morphology
Parodon magdalenensis is a small, elongate, fusiform characin reaching a documented maximum of 5 in standard length, per FishBase, with a maximum recorded weight of about 49 g — modest dimensions consistent with the rest of its scraper-feeding family. Like other Parodontidae, it has a subterminal mouth set on the underside of a somewhat pointed snout, armed with a row of small, flattened, spade-like teeth adapted for scraping rather than biting or grasping prey, and a streamlined, cylindrical-to-laterally-compressed body built for holding position in current.
Detailed pigmentation and fin-ray counts for this specific species are not covered in the sources consulted here, and the cache notes FishBase's account records breeding tubercles developing on the head and body of males — a form of sexual dimorphism common in riffle-dwelling characins that use tubercles for substrate contact or mate contests during the breeding season (see "Mating").
Habitat
This species is endemic to the Magdalena River drainage of Colombia, known from the La Miel River and its tributaries (including the type locality), the Paila River system, and tributaries of the upper Cauca River — all part of the wider Magdalena-Cauca basin that drains much of central and northern Colombia toward the Caribbean. As a member of Parodontidae, it is a classic riffle-and-run specialist: these fish are typically found holding station in flowing water over rock, gravel and wood substrates rather than in still backwaters, using their scraping mouths to graze the biofilm that coats submerged surfaces in fast-moving, well-oxygenated stretches.
Specific published water-chemistry data (temperature, pH, hardness) for Parodon magdalenensis were not found in the sources reviewed for this profile. Given the family's habitat and the Magdalena basin's tropical lowland-to-piedmont setting (the type locality sits at roughly 2362 ft elevation), a warm, well-oxygenated, moderately flowing freshwater environment is a reasonable inference, but no specific figures should be presented as confirmed.
Feeding
Parodontidae as a family are known by the common name "scrapetooths" for a reason: their diet centres on algae, biofilm and organic detritus rasped from rocks, wood and other submerged surfaces using specialised, flattened teeth. No stomach-content study specific to Parodon magdalenensis turned up in the sources reviewed here, but this feeding strategy is consistent across the genus and family, and there is no indication this species departs from it — it is a benthic grazer, not a predator or a fruit-and-seed opportunist like its distant pacu relatives.
In practical terms, a fish built this way spends its time working algae-covered surfaces in current rather than chasing food in open water, which should inform any attempt to replicate its diet in captivity (see "In the aquarium").
Mating
Very little is documented about courtship behaviour in Parodon magdalenensis specifically. FishBase records that males develop breeding tubercles, a form of external sexual dimorphism found in a number of riffle- and current-dwelling characins, which is consistent with reproductive biology described for the closely related río La Miel population by Pareja & Jiménez-Segura (2012) — cited in the Colombian Parodon taxonomy literature reviewed here — though the review does not spell out whether tubercles are used in male-male contests, substrate contact during spawning, or both.
No further detail on pairing behaviour, spawning triggers or courtship displays was found in the sources consulted, and none should be assumed; this remains a data-sparse area for the species.
Breeding
The precise breeding mode of Parodon magdalenensis is not clearly documented in the sources available for this profile. The Colombian taxonomy review cites reproductive-biology work on the río La Miel population (Pareja & Jiménez-Segura, 2012) and notes that males carry breeding tubercles, which hints at gonochoristic reproduction with some degree of substrate association or mate interaction, but it stops short of confirming whether this is an open-water egg-scattering characin or a species with more specific substrate or site behaviour. Most Parodontidae, and riffle-dwelling characins generally, are understood to be non-guarding egg-scatterers that broadcast eggs over gravel or rock in current, but that mode has not been confirmed here for this species specifically, and it should not be stated as fact.
There is no record in the sources reviewed of Parodon magdalenensis being bred in the aquarium hobby or commercially. This is, honestly, an unbred or essentially unknown-in-captivity species as far as available literature shows — a common situation for small, range-restricted South American riffle fish that have never entered the ornamental trade in numbers.
In the aquarium
Parodon magdalenensis is not an established aquarium fish, and none of the sources reviewed for this profile describe hobbyist experience keeping it. Given its biology, a suitable setup would need to replicate a flowing, well-oxygenated stream environment — a river-manifold or powerhead-driven current, a rock-and-wood substrate ideally allowed to grow a biofilm and diatom coating, and tankmates that are not aggressive competitors for the same grazing niche. At a maximum of 5 in, it is a modestly sized fish that would not need an especially large footprint, but its current and oxygenation requirements should not be underestimated for a riffle specialist.
Because it is essentially undocumented in captivity, any prospective keeper should treat husbandry as experimental and prioritise a diet of algae wafers, blanched vegetables and biofilm-supporting tank conditions over standard flake or pellet foods, mirroring its wild scraping diet. This is a fish for a specialist wanting to replicate a Colombian piedmont stream, not a community-tank staple, and its conservation status (see below) argues strongly against wild collection for the trade.
Conservation
Parodon magdalenensis has not been evaluated by the IUCN Red List (Not Evaluated, NE); no assessment for the species was located in the sources reviewed. This is unsurprising for a narrow-range Colombian endemic described as recently as 2011 and known only from a handful of tributaries within the Magdalena-Cauca system.
That narrow known range — limited to the La Miel River and tributaries, the Paila River system, and upper Cauca tributaries — is itself a conservation-relevant fact: single-basin endemics restricted to piedmont tributary streams are inherently more exposed to localised pressures such as damming, sedimentation, deforestation and water-quality change than widely distributed lowland species, even without a formal Red List assessment confirming a threat level. In the absence of a population assessment, no claim about trend or threat level should be asserted beyond what has been formally evaluated.