Taxonomy & naming
L255 is a code from the DATZ L-number system, started in 1988 for imported loricariids that could not yet be identified. It is a trade code, not a scientific name, and an undescribed form has no describing authority and no type specimens. The L-Wels registry lists the fish as Ancistrus cf. ranunculus "L 255". The cf. marks a tentative comparison with Ancistrus ranunculus (L34), not an identification, so the form remains Ancistrus sp. L255. PlanetCatfish files it as Ancistrus sp. (L255) and names no other code as the same fish. Trade names are Spotted Medusa Pleco and, in German, Weißpunkt-Froschkopf-Ancistrus (white-spot frog-head Ancistrus). The registry's bibliography includes the Welsatlas 2 and Miniatlas L-Welse (2005), Michael Hille's "Meine Ranunkeln", a DATZ 8/2009 press-review entry, and Daniel Konn-Vetterlein's account of the Rio Xingu bed.
Morphology
The registry gives about 5 in total length for L255. Diagnostic characters are not on record; "spotted" and the German "Weißpunkt" (white spot) in the trade names are labels, not a written description. Seven similar fishes are listed: Ancistrus macrophthalmus (LDA 74), Ancistrus ranunculus (L34), Ancistrus sp. "L 100" / "LDA 75", "São Felix", "Itaituba", "Breitkopf" and "L 514". How L255 is told apart from them is not on record.
Habitat
The registry places L255 in the middle Rio Xingu, about 93 mi south (upstream) of Altamira, in the state of Pará, Brazil, and classes the water as clearwater. No substrate or finer habitat details are on record for this code. Loricariids of this kind are generally associated with well-oxygenated water, current, and rock or wood cover; that is genus-level background, not a field observation for L255.
Feeding
The registry's diet class for L255 is predominantly herbivore, which in the aquarium means vegetable-based sinking foods and fresh vegetables. Whether it eats aquarium plants is not recorded. The class is a label for the form as a whole, not the result of a feeding study, and nothing on the natural diet of this form is on record.
Mating
The registry's sexing note is genus-level: male Ancistrus have more and larger tentacles on the head. Ancistrus are typically cave spawners, with the male guarding the eggs and larvae in the cave, and the registry rates cave requirements as standard for the genus. No courtship or spawning behaviour has been described for L255 specifically.
Breeding
The registry reports captive breeding of L255 and cites DATZ 8/2009 as the place where it was reported. It gives no details of that spawning, and clutch size, spawning site and fry development are not on record. The genus-typical pattern is cave spawning with male care of the eggs and larvae.
In the aquarium
The registry's keeping range is 79–86 °F and pH 5.0–7.0, with a tank about 31.5 in long recommended; this is aquarium guidance, not field data. Small groups are recommended, and a single fish is possible. As with other bristlenose catfishes, clean, well-oxygenated water and caves of rock or wood suit it, and territorial behaviour toward other plecos is common.
Conservation
L255 has not been assessed by the IUCN Red List and is Not Evaluated, because an undescribed form cannot be assessed until it has a name. For Brazilian export the registry notes that it is on Brazil's 2012 positive list (species cleared for ornamental export) and not on Brazil's 2020 negative list. Population size and trend are not on record. In general, collection for the trade and river engineering affect some L-number habitats.