Corydoras gracilis

Adults typically range from 3–4 cm in length. A distinctive feature of their coloration is a prominent arched black stripe that extends from the head to the very tail, contrasting with the light underside of the belly. This dark stripe is accentuated by a yellowish line above. Dark pigmentation is often observed at the base of the dorsal fin.

The species inhabits the central part of the Amazon basin in Brazil. In nature, it prefers small tributaries with dense riparian vegetation and an abundance of fallen leaves and branches on the bottom. The water in its habitats is usually acidic, with a characteristic brown tint due to the high content of tannins.

A peaceful and schooling species. In an aquarium, it is recommended to keep a group of 4–6 individuals to reduce stress levels, as the fish can be timid. It coexists well with other non-aggressive aquarium inhabitants of similar size.

The care of Corydoras gracilis is largely similar to the requirements for keeping other species of Cory catfish. Key aspects include maintaining clean and warm water, preventing the accumulation of organic waste, and providing a complete diet. Although the choice of decorations is usually not critical, in this case, it is recommended to recreate an environment resembling their natural habitat. It is desirable to have shelters, which can be branches, snags, and roots, as well as a leaf substrate at the bottom. The use of leaves from certain trees has a beneficial effect on the chemical composition of the water, helping to lower pH and increase the concentration of tannins. As for nutrition, a varied diet is crucial for maintaining the health of the fish. Their daily menu can consist of dry foods, supplemented with frozen or live foods such as brine shrimp, bloodworms, or daphnia. In terms of behavior and compatibility, these catfish feel more comfortable in a group consisting of 4–6 individuals. They get along well with peaceful and calm fish of similar size. However, it is worth avoiding proximity to territorial, and even more so, aggressive species.

An omnivorous species. In the aquarium, it is necessary to provide a varied diet, including high-quality sinking dry foods, as well as frozen or live foods such as bloodworms or tubifex. Fish should not feed exclusively on food remnants that have fallen to the bottom, as this does not provide complete nutrition.

For breeding, it is recommended to use a group with a predominance of males. Frequent water changes (50–70%) with cooler water and increased aeration serve as a stimulus for spawning. Eggs are laid on plant leaves or the aquarium glass. After spawning is complete, the parents should be removed to prevent them from eating the eggs. Fry begin to feed after the yolk sac is absorbed, requiring high water quality for survival.

This species is sensitive to water quality and substrate cleanliness. If kept on an unsuitable substrate, damage to the barbels is possible, which opens the way for bacterial infections. Prevention includes maintaining cleanliness, regular water changes, and using soft sand as a substrate. Caution should be exercised when catching them, as their stiff fin rays can inflict painful stings.

When purchasing, choose active fish with clean fins and undamaged barbels. Avoid individuals showing signs of emaciation, sunken bellies, or skin lesions. Healthy corydoras should show interest in foraging for food in the substrate and not exhibit signs of apathy or constant hovering at the water's surface.