Why are my newly bought Otocinclus dying suddenly?

Otocinclus are highly sensitive to shipping stress and often arrive at retailers underfed. If added to a sterile or newly cycled tank without sufficient algae and biofilm, they can easily starve. They also demand impeccable, stable water quality.

Will Otocinclus eat black beard algae or hair algae?

No. Otocinclus strictly prefer soft green algae, brown diatoms, and biofilm. They lack the mouthparts to tackle tough, fibrous algae like black beard (BBA) or long hair algae.

How many Otocinclus should I keep together?

You should keep a minimum of six Otocinclus. They are highly social, obligate shoaling fish that rely on a group for a sense of security. Solitary Otos will hide constantly and live shorter lives due to stress.

Do I need to feed my Otocinclus if my tank already has algae?

Yes. While they will eat the algae in your tank, a group of Otos can clear a small tank of soft algae in a matter of weeks. You must supplement their diet with blanched courgette, spinach, and high-quality sinking algae wafers.

Can I keep Otocinclus with a Betta fish?

Usually, yes. Otocinclus are incredibly fast and generally stay out of a Betta's way near the bottom or on the glass. However, ensure the tank is large enough (at least 60 litres for the Oto shoal) and monitor the Betta for extreme aggression.

FreshwaterTropicalIntermediate

Otocinclus Catfish

Otocinclus spp.

The Otocinclus Catfish is a diminutive, deeply peaceful algae grazer that makes a superb addition to mature planted aquariums.

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Ideal Conditions

Temperature: 21 – 26 °C
pH range: 6 – 7.5
Hardness: 2 – 15 dGH
Adult size: 3 – 5 cm
60 Litres for a small shoal: 60 litres+
Lifespan: 3 – 5 years
Diet: Herbivore/Aufwuchs Grazer
Water flow: moderate
Preferred setup: Densely planted with driftwood, leaf litter, and established biofilm.

About the Otocinclus Catfish

Generically traded as the 'Oto', this group encompasses several closely related Loricariid species, most notably Otocinclus macrospilus and O. vittatus. They are highly sought after in the aquatic hobby for their voracious appetite for soft green algae and diatoms. Unlike the common plecostomus, Otocinclus remain incredibly small and will not damage delicate plant leaves or uproot hardscape. They are an elegant, natural solution to algae control in thoughtfully maintained setups.

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Is it right for your tank?

Check Otocinclus Catfish against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Otocinclus Catfish comes from

Native range

Amazon Basin, Orinoco Basin, Paraná Basin

Countries / regions

Brazil, Colombia, Peru, Venezuela, Argentina

Habitat

Well-oxygenated, shallow margins of slow-to-moderate streams with dense aquatic vegetation and submerged wood.

Trade 'Otocinclus' generally consists of O. macrospilus and O. vittatus exported from Peru and Colombia.

Similar species

Pygmy Corydoras
Corydoras pygmaeus
Siamese Algae Eater
Crossocheilus oblongus
Bristlenose Pleco
Ancistrus spp.

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Neon Tetra
Paracheirodon innesi
Both species are incredibly peaceful, require similar water parameters, and occupy different levels of the aquarium.
Great
Cherry Shrimp
Neocaridina davidi
Otocinclus are one of the few fish completely safe with dwarf shrimp and their fry, showing no predatory instinct towards them.
Great
Corydoras Catfish
Corydoras spp.
Excellent peaceful companions that share the bottom zones without displaying territorial aggression.
Great
Angelfish
Pterophyllum scalare
Adult Angelfish may attempt to eat small Otocinclus. Because Otos have spiny pectoral fins, they can become fatally lodged in the larger fish's throat.
Compatible with caution
Siamese Algae Eater
Crossocheilus oblongus
Can be highly boisterous during feeding and may outcompete the shy Otocinclus for essential food and algae resources.
Compatible with caution
Goldfish
Carassius auratus
Goldfish require drastically different temperatures, produce too much waste, and will easily swallow an adult Otocinclus.
Not recommended

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