Corydoras duplicareus

Corydoras duplicareus is considered the "twin" of Adolfo's cory: the cream-white body, the black band running over the eye and the orange patch on the nape are present in both species. The difference lies in the black band on the back: in duplicareus this band is about twice as wide, covering the upper part of the back from below the dorsal fin to the caudal peduncle and spilling over onto the sides. In adolfoi it remains a thin stripe.

Adults reach 5–6 cm. Its care is the same as for adolfoi; since it comes from blackwater, it needs clean, stable water.

It lives in blackwater tributaries in the upper Rio Negro basin. These waters are darkened by tannins released from leaves and roots, and are very soft and acidic; the bottom is fine sand and leaf litter.

• Volume: at least 60 liters for a group of 6–10.
• Substrate: fine, soft sand; a few dried leaves provide a natural look and tannins.
• Water: 22–26°C; pH 5–7, soft water. Avoid sudden changes in pH and temperature.
• Maintenance: 20–30% water change weekly, low nitrate. It should go into a mature aquarium.

Sinking granules and tablets, frozen bloodworms, brine shrimp, daphnia. Feed wild-caught fish frozen food first and gradually get them used to dry food. Make sure the food reaches the bottom.

A peaceful, calm and social bottom dweller. In a large group it forages in the open throughout the day; kept in small numbers it becomes timid.

Good companions: cardinal tetra, neon tetra, rummy-nose tetra, pencilfish, apistogrammas, otocinclus.

Avoid: cichlids that claim the bottom, large and greedy fish, species that need hard water.

At least 6, ideally 10 or more individuals. If a mixed group with adolfoi is formed, they roam together; however, separate groups are better for keeping the species pure. For breeding, 2 males per female are recommended.

It is bred in the aquarium; the same approach as for adolfoi applies. Soft, acidic water, plenty of live or frozen food and a slightly cooler water change encourage spawning. The eggs are stuck to the glass and leaves and hatch in 3–5 days. Since the eggs are sensitive to fungus, clean water with gentle flow helps when they are moved to a separate container.

• Acclimate slowly after shipping; blackwater species are sensitive to sudden changes.
• Barbel erosion: dirty or sharp substrate.
• It is sensitive to salt and copper-based medications.
• Quarantine: observing newly arrived fish in a separate aquarium for 2–3 weeks prevents diseases from being carried into the main aquarium.

Viewed from above, females are broader, plumper and slightly larger. Males are slimmer.