Taxonomy & naming
The registry files the fish as Hemiancistrus cf. subviridis “L 128”. The cf. is a tentative comparison, not an identification: the atlas’s Hemiancistrus subviridis page is for the described species, which the registry codes L200 and the trade calls the green phantom. PlanetCatfish lists this fish as Hemiancistrus sp. (L128), with no related or same-fish code. Trade names are the German Blauer Phantomwels and Blue Pleco, and Blue phantom pleco is the common name on record. The bibliography runs to the Welsatlas 2, the Miniatlas L-Welse, an article on another phantom catfish from Colombia, a note on the water zones of the Río Tomo, and several press reviews.
Morphology
More than 10 in total length is the registry’s figure; no measured maximum is on record. Diagnostic characters are not set out, and an undescribed form has no formal diagnosis to cite. Blue Phantom suggests bluish colouring, but it is a trade label, not a measured character. Similar fishes listed by the registry are Baryancistrus demantoides (L200), Hemiancistrus subviridis (L200), Hemiancistrus cf. subviridis “L 476”, Guyanancistrus cf. longispinis “Amapa” and Ancistrini sp. “LDA 39”.
Habitat
The registry records the Río Orinoco drainage near Puerto Ayacucho (Amazonas, Venezuela) and Puerto Carreño (Vichada, Colombia), which is why the fish is listed under both countries. The water is classed as clearwater. No substrate or habitat-place details are recorded. Ancistomus cf. sabaji “L 124”, Pterygoplichthys gibbiceps (L165) and Guyanancistrus guahiborum (L106) are listed as fishes found together with L128.
Feeding
L128 is classed as mainly a herbivore, though whether it will eat aquarium plants is not recorded. Keepers feeding a herbivorous pleco typically offer vegetable matter, such as blanched vegetables, and plant-based sinking foods. No wild diet data are on record, and the registry names no particular foods, only the dietary class. For a herbivore that grows large, vegetable matter is the basis of any feeding plan.
Mating
For sexing, the registry gives a genus-level pointer for Hemiancistrus: check head shape, body shape and pectoral fins, since males have a more angular head and females a broader waist. Cave behaviour is listed as the genus standard, and Hemiancistrus are typically cave spawners in which the male guards the eggs and larvae. Nothing about courtship is documented for this code.
Breeding
Captive breeding has been reported (the registry cites Zoo Berlin), with no further details of the spawning. Clutch size, egg and fry development, and any triggers are not on record, nor is it stated how often the fish has been bred. None of the bibliography titles mentions breeding.
In the aquarium
Registry keeping figures are 77–84 °F and pH 5.5–7.5, with a recommended tank length of 59 in, in line with a fish of more than 10 in — aquarium figures, not field measurements. Small groups are recommended, though a single fish is possible. Typical needs apply: clean, well-oxygenated water with current, and rock or wood caves. Territorial behaviour toward other plecos is common.
Conservation
L128 is Not Evaluated by the IUCN, and cannot be assessed while it lacks a name of its own. The registry gives no export-list status for it. Collection for the trade and river engineering affect some L-number habitats in general, but nothing is documented about the Orinoco populations of this form.