Hoplisoma duplicareus

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Hoplisoma duplicareus, also known as Corydoras duplicareus, is a small South American catfish valued for its elegant appearance and peaceful behavior. Native to the Rio Negro basin in Brazil, it inhabits soft, acidic waters often tinted by tannins. Its pale body is highlighted by a dark facial mask and a characteristic orange coloration behind the head. Like other corydoras, it explores the bottom with its barbels and benefits from being kept in a group. This species is collected from the wild and remains very common in the aquarium trade, but it requires stable water, a soft substrate, and an appropriate diet.

General species description

Hoplisoma duplicareus is a small, schooling bottom-dweller belonging to the family Callichthyidae. It spends much of its time sifting through the substrate, alone or in a group, in search of food. Its behavior is generally peaceful and sociable, making it suitable for a well-planned community aquarium. It should be kept in groups of at least six, preferably more, to encourage natural behavior and reduce shyness. The species is especially active during calm periods, although it may also move through the water column from time to time. Like its relatives, it has sensitive barbels that help locate food. A mature, well-oxygenated and well-maintained aquarium is preferable. Filtration should provide good water quality without creating an excessively strong current at the bottom. Its popularity comes from its contrasting pattern, small size, and compatibility with many small Amazonian fishes.

Geographic origin and biotope

Country of reference: Brazil. Hoplisoma duplicareus comes from the Rio Negro basin in northwestern Brazilian Amazonia, particularly the Rio Unini area. It inhabits forest streams with soft, acidic water that is generally low in minerals. Leaves, wood, and decomposing plant material often release tannins into the water, producing an amber to brown coloration. The habitat is shaded by riverside forest, with subdued light and varying amounts of plant debris covering the bottom. The fish usually occupies calm or gently flowing areas with fine sand and fallen leaves. In an aquarium, soft to moderately soft water, moderate lighting, and properly prepared roots or leaves provide a closer approximation of its environment. Stability matters more than constantly pursuing extremely acidic water. A non-abrasive substrate protects its barbels while it searches for food.

Precise locality and local name

The locality generally associated with Hoplisoma duplicareus is the Rio Unini, a tributary of the Rio Negro, near Barcelos in Amazonas State, Brazil. This region forms part of a large network of forest rivers where seasonal changes affect water levels and the amount of plant debris available. In the aquarium trade and among hobbyists, the most commonly used name remains Corydoras duplicareus, although current classification places the species in the genus Hoplisoma. No widely established Brazilian vernacular name is commonly used for this species in the aquarium hobby. It is sometimes confused with Hoplisoma adolfoi, which it closely resembles, especially in its facial mask and orange band. Careful identification should consider the complete color pattern, body shape, and stated locality rather than relying on a single visual feature.

Appearance and physical characteristics

Hoplisoma duplicareus has a compact body protected by two rows of bony plates, typical of corydoras. Its base color is pale, ranging from creamy white to silvery gray, with a black band crossing the eye region. An orange to copper-colored area appears behind the head and extends toward the dorsal region, while a broad dark marking is visible on the rear part of the body. The fins are generally translucent, with darker tones on the dorsal and caudal fins. The lower mouth bears barbels used to locate food in the substrate. As in other members of the group, the pectoral and dorsal fins have locking spines, so the fish should be handled carefully. Adult size remains modest, at about 5 cm in total length, with females usually being broader and more robust than males.

General diet

In the wild, Hoplisoma duplicareus searches for small organisms, larvae, worms, tiny crustaceans, and other edible particles in sand and bottom debris. It is not a cleaner that can survive on leftovers missed by other fish. In an aquarium, provide a complete diet that reaches the substrate directly. Quality sinking tablets, pellets designed for bottom-dwelling fish, and frozen foods such as mosquito larvae or brine shrimp are suitable. A varied diet supports good condition and prepares the fish for breeding. Meals should be generous enough for every individual to eat, especially in a community aquarium. Avoid food that is too large or tablets that break down poorly. A varied diet rich in aquatic animal protein, offered in small portions, supports growth without unnecessarily polluting the water. Live or frozen foods often stimulate activity and natural foraging behavior.

Essential data

• Native river: Rio Unini, Rio Negro basin
• Local name used: Corydoras duplicareus
• Origin of the scientific name: Hoplisoma is the current genus; duplicareus identifies the species
• Full-name etymology: Hoplisoma comes from Greek and refers to an armored body; duplicareus means doubled or double
• Common/vernacular names: Corydoras duplicareus; masked cory
• Family: Callichthyidae
• Subfamily: Corydoradinae
• Name pronunciation: hop-li-SO-ma - du-pli-ka-REE-us
• Discovery: Isaäc J. H. Isbrücker and Han Nijssen, 1983
• Maximum adult size: About 5 cm
• Water temperature and pH: 22 to 28 °C; pH 5.0 to 7.5
• Stream appearance and surrounding vegetation: Shaded forest waters, tannin-stained, with fallen leaves, roots, and dense riparian vegetation
• Typical tankmates: Hoplisoma adolfoi, Paracheirodon axelrodi, Hoplisoma sterbai
• Temperament and behavior: Peaceful, schooling, active on the bottom, and occasionally prone to brief trips to the surface
• Water depth: Shallow to intermediate areas of forest streams
• Sexual dimorphism: Females are broader and more robust; males are generally smaller and slimmer
• Bottom structure and flow: Fine sand, leaves, and wood; low to moderate current

In your aquarium. To keep Hoplisoma duplicareus successfully, provide a good-sized group, fine sand without sharp edges, and clean, stable, well-oxygenated water. Roots, leaves, and shaded areas will help the fish feel secure. Offer a varied sinking diet so every fish receives food without excessive competition. Because this is a wild-collected species, careful acclimation and sensible quarantine are especially worthwhile. Regular maintenance, moderate water changes, and observation of the barbels can help reveal substrate or water-quality problems early.