Otocinclus negros

Adults of this species grow to approximately 3 cm in length. Their dark coloration, varying from gray to brownish, allows them to effectively camouflage themselves among plant thickets, hiding from potential predators. Hard coverings, covered with small spines, provide additional protection for the body. Through evolution, the fish's mouth has acquired a sucker shape and is now located on the underside of the head, which is an adaptation to its feeding habits.

In nature, the species inhabits rivers of the Paraguay basin, specifically the Piribebuy and Aguará Guazú rivers. The fish prefer shallow areas with slow currents, dense aquatic vegetation, and an abundance of organic substrates such as submerged snags and tree roots, which serve as shelter and a food source.

These catfishes prefer to live in groups of their own kind; when alone, they can become timid and more reclusive. Otocinclus negros get along well with many peaceful fish species of comparable size. Such tank mates can include Corydoras, Tetras, small Cyprinids (e.g., Danios and Rasboras), dwarf cichlids, and other representatives of the Otocinclus genus.

For a group of 8–10 catfishes, an aquarium with a volume of 40 L or more will be most suitable. When setting up the tank, provide areas with dense plant thickets and accumulations of driftwood. Dim lighting is recommended, and floating vegetation will effectively create the necessary shading. Since Otocinclus negros are from subtropics, they require relatively cool water, with a temperature not exceeding 23–24°C. These catfishes are very sensitive to the accumulation of organic waste, so the aquarium requires regular maintenance, including weekly partial water changes with fresh water, and a properly functioning filtration system.

The diet of these fish in their natural environment consists mainly of algae and small organisms living on them. In a home aquarium, it is crucial to provide access to appropriate food sources. These can be specialized plant-based foods in the form of tablets, wafers, or flakes based on algae. Pieces of green vegetables and fruits, such as spinach, zucchini, or blanched peas, are also suitable. Small invertebrates, such as fresh or frozen brine shrimp, bloodworms, and daphnia, will be a valuable addition to the diet. Placing natural driftwood in the aquarium is welcomed, as it often serves as a natural environment for algae growth.

Breeding occurs in pairs or groups. Spawning is stimulated by a partial water change with cooler water, which mimics the rainy season. The female lays eggs on plant leaves or hard surfaces, after which the male fertilizes the clutch. The parents do not show care for their offspring. Fry begin to feed on infusoria and specialized foods a few days after hatching.

Fish are sensitive to water quality and the accumulation of nitrogenous compounds. Characteristic problems include bacterial infections of the skin and fins, which arise from poor keeping conditions. Prevention includes weekly water changes, maintaining stable parameters, and avoiding overfeeding, as excess organic matter promotes the development of pathogenic microflora.

When purchasing, choose active individuals with a rounded, but not bloated, belly, which indicates good nutrition. It is important to avoid fish with sunken bellies, as this is a sign of emaciation. Inspect the body for damage, white film, or ulcers. In the store, fish should show interest in foraging for food on decorations or glass.