Black Otocinclus Care Guide - Aquarium Setup, Diet & Breeding

Black Otocinclus are tiny, laterally flattened suckermouth catfish with dark markings over a brown, olive or blackish body. Their armour-plated appearance, alert eyes and constantly working mouth give them the characteristic look of miniature algae-grazing loricariids. Colour intensity varies with mood, background and water conditions.

This species is peaceful, active and highly observant, spending much of its time attached to leaves, wood, rocks and aquarium glass. It is not an aggressive fish, although individuals can become shy when kept alone or housed in a busy environment. Groups display more natural confidence and activity.

In the wild, Black Otocinclus inhabit shallow streams and small rivers where submerged plants, branches and stones support a coating of algae, microorganisms and biofilm. Their sucker-like mouth is adapted for scraping these surfaces rather than for hunting larger prey.

Hisonotus notatus belongs to the small loricariid catfish group often sold under the broad name Otocinclus. Despite their modest size, they are sensitive, specialised grazers whose long-term health depends on access to natural grazing surfaces and stable conditions.

Black Otocinclus, Hisonotus notatus, originates from coastal freshwater rivers and streams in southeastern Brazil, particularly in the states of Rio de Janeiro and São Paulo. It is a South American loricariid associated with clear, gently flowing waters and marginal vegetation.

A group of Black Otocinclus should have at least a 45-litre aquarium, with a footprint of roughly 60 cm by 30 cm or larger. Use mature filtration with gentle flow, excellent oxygenation and stable, clean water. Provide broad-leaved plants, driftwood, smooth stones and shaded retreats that develop natural biofilm, together with a soft sand or fine rounded-gravel substrate that will not damage their underside. A mature, well-established aquarium is preferable to a newly set-up tank.

Up to about 4 cm (1.6 in) in total length. Females are usually slightly larger and deeper-bodied than males.

Their diet should centre on algae, biofilm and other plant matter collected from aquarium surfaces. Offer algae wafers or specialised herbivore foods, along with blanched courgette, cucumber, spinach or green beans, while removing uneaten vegetables promptly. A varied diet can occasionally include small amounts of protein-rich foods, but frequent heavy feeding of meaty foods is unsuitable for this primarily grazing species.

Black Otocinclus are suitable for calm community aquariums containing small tetras, peaceful rasboras, gentle livebearers, pencilfish, small Corydoras and other non-aggressive dwarf catfish. They can also be kept with peaceful shrimp and snails. Avoid large, boisterous or predatory fish, fin-nippers and aggressive bottom dwellers, which may outcompete, injure or intimidate them.

Black Otocinclus are egg scatterers that may spawn when mature fish are well conditioned with abundant natural biofilm and varied foods. The female deposits small adhesive eggs on plant leaves, aquarium surfaces or other cover, with the male fertilising them soon afterwards. Eggs usually hatch within a few days, and the fry need mature, algae-rich surroundings, microscopic foods and very gentle filtration. Remove adults or protect the eggs if predation becomes a problem.

Females are generally broader through the abdomen and grow slightly larger, particularly when carrying eggs. Males are usually slimmer and a little smaller, with no dramatic difference in colouration.