Mid-Stripe Otocinclus (Otocinclus affinis) Care Guide
Otocinclus affinis is a small dwarf suckermouth catfish from the Rio de Janeiro region of Brazil, a peaceful shoaling algae grazer for mature, planted tanks.
Compiled by Aquairi from published sources · Published · Updated
Overview
Otocinclus affinis (also placed in the genus Macrotocinclus) is a dwarf suckermouth catfish of the family Loricariidae (subfamily Hypoptopomatinae). It is a long-established aquarium "oto" and is often confused with similar Otocinclus species. FishBase gives a maximum standard length of about 5 cm.
Taxonomy
- Family: Loricariidae
- Scientific name: Otocinclus affinis
- Subfamily: Hypoptopomatinae
- Common synonyms: Golden Oto
Habitat
FishBase records the species from the vicinity of Rio de Janeiro, Brazil. Otos inhabit well-oxygenated streams and river margins, living in shoals and clinging to wood, stones and broad-leaved plants where they feed on the surface film. The genus has an air-breathing adaptation for low-oxygen periods.
Tank requirements
- Minimum tank volume: 60 L (16 gal)
- Adult size: 3-4 cm (1.2-1.6 in)
- Temperature: 24-28 °C (75-82 °F)
- pH: 6-7.5
- GH: 2-12 °dGH
- Group size: ≥6 individuals
- Lifespan: 8-12 years
Diet
The diet is algae-based, centred on diatoms and aufwuchs. It thrives in a mature, planted tank offering a continuous supply of soft green algae and biofilm, supplemented by blanched vegetables and algae wafers. Animal foods play only a minor role.
Compatibility
A peaceful, retiring fish, it is easily outcompeted by boisterous tankmates and should be housed with calm species. It is a social shoaler best kept in groups of at least six and is fully plant-safe, suiting communities of small tetras and Corydoras.
Breeding
As with other otos, the genus lays adhesive eggs that are not guarded, scattering them on plants and glass. Cooler, generous water changes are reported to encourage spawning.
Conservation status
The IUCN Red List assessed the species as Least Concern (2018).
Breeding Otocinclus affinis
Overview
Otocinclus affinis is a dwarf member of the family Loricariidae. Genus members are specialised algae and aufwuchs grazers and live in shoals. Unlike many other loricariids, in which the male builds and guards a nest, Otocinclus lay adhesive eggs and do not guard them. The genus ranges through lowlands from northern Venezuela to northern Argentina but is generally absent from the Amazon and Orinoco lowlands, and the fish primarily feed on algae or aufwuchs on roots, stones, macrophytes and broad-leaved grasses. Detailed species-specific breeding records for O. affinis are scarce, so the information below describes the reproductive pattern documented across the genus.
Sexing
Sexual dimorphism is subtle. When the fish are viewed from above, mature females appear broader in the body than males. There are no reliable external colour differences reported for the genus.
Conditioning
Otocinclus feed almost exclusively on algae and other green matter. Conditioning relies on a mature tank with abundant biofilm and soft algae plus supplementary vegetable foods, keeping a shoal of six or more so a compatible pair can form.
Spawning Behavior & Trigger
Spawning resembles that of Corydoras: the pair adopts the classic 'T' position, in which the male grasps the female between his pectoral fin and her body while eggs and sperm are released. Large weekly water changes with cooler water appear to be an important trigger, mimicking seasonal rainfall. The presence of another actively breeding species in the tank (Corydoras are commonly cited) may also help stimulate spawning.
Egg & Fry Care
Unlike Corydoras, the eggs are scattered fairly randomly, usually among plants in the upper part of the tank or on the aquarium glass; they are adhesive and receive no parental care. The fry are very tiny and require access to copious amounts of algae and other green matter once free-swimming.
Common Challenges
Otocinclus are considered difficult to breed in captivity, and most fish in the trade are wild-caught. The main obstacles are establishing a robustly mature, algae-rich system, reliably sexing and pairing the fish, and providing enough microscopic food for the minute fry.