Taxonomy & naming
L120 is a code from the DATZ L-number system, begun in 1988 to label imported loricariids not yet identified to species. It is a trade code, not a scientific name; an undescribed form has no describing authority and no type specimens. The L-Wels registry lists it as Ancistrus sp. "L 120", and PlanetCatfish files it as Ancistrus sp. (L120) and treats L182 as the same fish. Trade names are Black Fin Bristlenose, the German Goldpunkt-Riesenantennenwels (gold-spot giant bristlenose) and, in English, Starlight bristlenose pleco, a name the atlas also lists for the described Ancistrus dolichopterus (L183). The registry also carries the label "Ancistrus puncatatus", spelled as it appears there, which is a historical trade label and not an identification. Its bibliography includes the Welsatlas 2 and Ingo Seidel's Back to Nature handbook for L-catfishes (2008).
Morphology
The registry gives about 10 in total length for L120. Its diagnostic characters are not on record and there is no written description; the names black fin, gold-spot and starlight are trade labels, not measured characters. One similar fish is listed, Ancistrus sp. "Río Ucayali". Like other Ancistrus it is a suckermouth armoured catfish whose body is covered in bony plates.
Habitat
The registry says only that L120 is exported from Guyana. No river, drainage or collection point is on record, and the water type is not given. The usual loricariid needs — clean, well-oxygenated water, current, and rock or wood cover — are genus-level background, not observations for L120.
Feeding
The registry classes L120 as predominantly herbivorous and notes that it eats aquarium plants, which matters in a planted tank. Aquarium feeding therefore centres on vegetable matter: algae-based sinking wafers, fresh vegetables and similar foods, and delicate live plants may be grazed. The natural diet is not recorded; the registry gives a diet class, not a feeding study.
Mating
Sexing follows the genus. The registry's note, given at genus level, is that male Ancistrus carry more and larger tentacles on the head than females. Ancistrus are typically cave spawners: the male holds a cave and guards the eggs and larvae there, and the registry rates the cave requirement as standard for the genus. Nothing specific to L120 is described beyond the bare record of captive breeding.
Breeding
The registry marks L120 as bred in aquaria. It gives a plain yes, with no source, number of spawnings or method, so clutch size, spawning site and fry development remain unknown. The genus-typical pattern is cave spawning with the male caring for eggs and larvae, but none of that is documented for this form.
In the aquarium
The registry's guidance for L120 is 77–84 °F, pH 5.0–7.0 and a tank about 59 in long; this is aquarium guidance, not field data. Small groups are recommended, though a single fish is possible. Like other bristlenose catfishes it does best in clean, well-oxygenated water with caves of rock or wood, and territorial behaviour toward other plecos is common. The registry notes that it eats aquarium plants, so soft-leaved species in a planted tank may be grazed.
Conservation
L120 has not been assessed by the IUCN Red List and is listed as Not Evaluated, since an undescribed form cannot be assessed until it has a name. With no locality on record beyond the country, nothing can be said about threats to this particular form. In general, collection for the trade and river engineering affect some L-number habitats.