Otocinclus Negros (Otothyropsis piribebuy) Med-Large - Aquarium Glaser

Otocinclus Negros is a small, brown/black-bodied algae-eating catfish from South America, highly valued in planted aquariums for its peaceful nature and effectiveness at grazing soft algae and biofilm.

Scientific & Trade Background

• Trade name: Otocinclus Negros
• Current scientific name: Otothyropsis piribebuy (formerly Otocinclus sp. “Negros”) 
• Family: Loricariidae (armoured catfish)
• Common names: Brown Otocinclus, Black Otocinclus, Brauner Ohrgitterharnischwels

This species was long imported under the Otocinclus name but was formally separated taxonomically after scientific description. 

Origin & Natural Habitat

• Distribution: Paraguay River basin (Paraguay, northern Argentina, southern Brazil) 
• Habitat:
  • Shallow, plant-rich rivers and streams
  • Moderate current and high oxygen levels
  • Abundant submerged wood and biofilm

Size & Appearance

• Adult size: ~3–4 cm (1.25–1.6") 
• Body color: Dark brown to grey-black, lighter underside
• Body type: Slender, armored with bony plates
• Mouth: Downturned suction mouth for grazing algae and biofilm

Compared to common Otocinclus vittatus, Negros appear darker, more cryptic, and slightly more elongated.

Temperament & Behavior

• Temperament: Very peaceful
• Activity: Diurnal (active during the day)
• Social needs: Strict schooling species — minimum 5–6, ideally 8–10+ individuals 

When kept singly or in pairs, they become shy and stressed and may fail to feed properly.

 Aquarium Care Requirements

 Tank Size

• Minimum: ~40–55 L (10–15 gallons) for a group
• Best suited to mature, planted aquariums with visible algae growth

Water Parameters

• Temperature: 18–24 °C (64–75 °F) – prefers cooler water than many tropical fish 
• pH: 5.5–7.5
• Hardness: 2–15 dGH
• Flow: Gentle to moderate
• Water quality: Extremely sensitive to ammonia, nitrite, and nitrate buildup

Not suitable for brand-new aquariums — these fish rely heavily on established biofilm.

Diet & Feeding

• Primary grazers of:
  • Soft green algae
  • Brown diatoms
  • Biofilm on plants, glass, and wood 

Must be supplemented once algae is depleted:

• Algae wafers (high spirulina content)
• Blanched vegetables (zucchini, cucumber, spinach)
• Occasional frozen foods (daphnia, cyclops)

Poor feeding is the #1 cause of early mortality in Otocinclus species. 

Compatibility

Excellent tankmates:

• Small tetras
• Rasboras
• Pygmy Corydoras
• Dwarf shrimp (Amano, Neocaridina)

Avoid:

• Large or aggressive fish
• Boisterous feeders that outcompete them
• Copper-based medications (highly sensitive)

Breeding

• Rare but possible in well-established aquariums
• Eggs are deposited on leaves, glass, or hard surfaces
• No parental care
• Fry are extremely small and require biofilm-rich environments