Pseudolithoxus kelsorum L-189

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Pseudolithoxus kelsorum L-189 is a rheophilic loricariid that remains uncommon in specialized aquariums. Associated with the L-189 code, this fish is recognized by its flattened body, current-adapted fins, and discreet behavior on rocky surfaces. It comes from the Orinoco basin in Venezuela, where it inhabits well-oxygenated flowing water. This wild-collected species requires careful acclimation and stable water conditions. In the aquarium, it is best suited to a mature setup with plenty of cover, strong circulation, and regular plant-based foods.

General species description

Pseudolithoxus kelsorum L-189 belongs to the loricariids specialized for flowing water. Its ventrally flattened body and sucker mouth allow it to remain attached to rocks despite the current. It is mainly bottom-dwelling and often becomes more active as the aquarium lights go out. The trade code L-189 is still widely used by aquarists, even though the species has since been scientifically described. Its intermediate rarity in the hobby—uncommon without being exceptional—makes it appealing to loricariid keepers. Wild specimens may be sensitive to transport, sudden temperature changes, and poor oxygenation.

Geographic origin and biotope

This species comes from the Orinoco basin in Venezuela, in tropical waterways with noticeable current. Its natural habitat is associated with rocky areas, constant water movement, and high oxygen levels. The bottom is generally made up of stones, gravel, and locally deposited sand. Dense aquatic vegetation is less important than the algae and biofilm covering exposed surfaces. In captivity, a long aquarium with strong circulation, smooth rocks, wood, and sheltered resting areas is appropriate. Because the available population is wild-collected, gradual acclimation is especially important.

Precise locality and local name

Pseudolithoxus kelsorum L-189 is associated with rocky tributaries of the Orinoco system in Venezuela. L-189 is the main identifier used by aquarists and importers. No broadly established local vernacular name is used for this species; in the specialized trade, it is mainly known as L-189 or Pseudolithoxus kelsorum. This designation is useful because Pseudolithoxus species can look similar when young or when kept under different conditions. To preserve reliable identification, collection details and the L-189 code should be kept with the fish.

Appearance and physical characteristics

The body of Pseudolithoxus kelsorum L-189 is low, elongated, and strongly adapted to life on the bottom. As in several rheophilic loricariids, its ventral mouth forms an effective sucker, while the pectoral and pelvic fins help it stabilize on rocks. Overall coloration is usually dark, with brownish to grayish tones and a subtle pattern that provides camouflage. Bony plates protect the body, and the head is robust and flattened. Color details can vary with age, stress, and lighting. Its **flattened body shape** and ability to cling to the substrate are its most notable aquarium characteristics.

General diet

Pseudolithoxus kelsorum L-189 mainly grazes on biofilm, fine algae, and microorganisms growing on surfaces. In the aquarium, its diet should include quality vegetable wafers, spirulina-based foods, and blanched vegetables such as zucchini or cucumber. A regular source of **fiber and plant matter** is essential, although small amounts of more protein-rich food may occasionally be offered. Feed after the lights go out, when the species is more active. A mature aquarium where rocks and wood carry natural biofilm also supports its grazing behavior. It should not be treated simply as an algae-eating clean-up fish.

Essential data

• River of origin: Orinoco and associated river network
• Local name used: L-189
• Origin of the scientific name: Pseudolithoxus refers to a loricariid resembling a stone fish; kelsorum honors the Kels family
• Etymology of the full name: Pseudo means false or resembling; lithos means stone in Greek; kelsorum is dedicated to the Kels family
• Common/vernacular names: L-189, L-189 river loricariid
• Family: Loricariidae
• Subfamily: Hypostominae
• Name pronunciation: soo doh lith oh ksoos kel SOR oom
• Discovery: Jonathan W. Armbruster and Francisco Provenzano, 2000
• Maximum adult size: about 13 cm
• Water temperature and pH: 25 to 29 °C; pH 6.0 to 7.5
• Stream appearance and surrounding vegetation: clear to moderately tinted, rocky, well-oxygenated streams; tropical riparian vegetation
• Typical tankmates: other small rheophilic fishes from the Orinoco basin, current-loving characins, and similarly sized loricariids
• Temperament and behavior: peaceful, discreet, bottom-dwelling, and more active at dusk; appreciates cover and current
• Water depth: shallow to moderately deep sections
• Sexual dimorphism: external differences are subtle; mature males may have a more robust body shape
• Bottom structure and flow: rocks, gravel, and localized sand; moderate to strong flow with high oxygenation

In your aquarium

Success with Pseudolithoxus kelsorum L-189 depends on clean, warm, highly oxygenated water and constant but not excessive circulation. Provide several rocky shelters, wood, and surfaces where biofilm can develop. Feed regularly after the lights go out and monitor body condition, especially after introducing a wild specimen. Avoid competition from overly fast or aggressive fish. Efficient filtration, consistent water changes, and slow acclimation are the key elements for keeping this **rheophilic loricariid** successfully over the long term.