Corydoras sp. C123, commonly known as the Yellow Corydoras, is an undescribed Corydoras species from the western Amazon Basin, most closely associated with the Rio Nanay drainage in northeastern Peru. It inhabits shallow, slow-moving streams and marginal floodplain areas with sandy substrates, scattered leaf litter, and submerged roots, where water is typically soft, warm, and lightly stained. These environments are calm and structurally complex, allowing groups to forage continuously across open sand and shaded edges. Adult Corydoras sp. C123 typically reaches around 2 to 2.5 inches in length. The body shows a dark gray to brown base coloration with distinct horizontal striping along the flanks, becoming more pronounced toward the rear of the body. The head is darker and more uniformly shaded, lacking heavy spotting or reticulation. The most defining visual feature of this species is its bright yellow fins, including the caudal, dorsal, pectoral, and pelvic fins. The dorsal fin often shows dark spotting or barring over a yellow background, while the caudal fin is strongly yellow with darker banding near the base. The contrast between the striped body and vivid yellow fins gives this species a bold, high-contrast appearance that is immediately recognizable. A tank of at least 20 gallons with ample bottom space is recommended for a proper group. Fine sand is strongly preferred to protect the barbels and allow natural sifting behavior. Driftwood, leaf litter, and gentle hardscape elements help recreate the shaded, debris-rich habitats they occupy in the wild, while still leaving open areas for active foraging. Low to moderate flow with good oxygenation is ideal. Water conditions should reflect their Amazonian origin, with temperatures between 72 and 79°F, a pH of approximately 6.0 to 7.2, and soft to moderately soft water. Like all Corydoras, this species is sensitive to poor water quality and accumulated waste at the substrate level, making regular water changes and clean sand essential. Feeding is straightforward. Corydoras sp. C123 feeds on insect larvae, small crustaceans, worms, and organic material in nature. In the aquarium it readily accepts sinking micro-pellets, frozen bloodworms and daphnia, baby brine shrimp, and fine prepared foods. It should be deliberately fed and not expected to subsist on leftovers. Corydoras sp. C123 is peaceful and highly social and should be kept in groups of six or more to display natural behavior and confidence. It mixes well with small, calm community fish such as tetras, rasboras, pencilfish, and dwarf cichlids that share similar water preferences. Breeding behavior follows typical Corydoras patterns but is not widely documented. Spawning involves group activity and egg placement on hard surfaces such as glass, plants, or wood. Cooler water changes and high oxygen levels may help encourage spawning. Corydoras sp. C123 is a striking, active, and visually distinctive Corydoras defined by its horizontal striping and vivid yellow fins, making it an excellent choice for peaceful Amazonian community aquariums with soft substrates and stable water conditions.
