Golden otocinclus
Otocinclus affinis
Otocinclus affinis is a small South American suckermouth catfish prized for grazing soft algae and biofilm on plants, glass, and décor. It has a slender body with a dark lateral stripe and a pale underside, and it is best kept in groups where it feels secure. Although peaceful, it can be delicate when newly imported and does best in mature, well-oxygenated aquariums with plenty of natural growth to graze.
The Golden otocinclus features a slender, olive-green body adorned with golden hues and distinctive dark spots along its back.
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Quick Facts
Size
5.0 cm
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
15 gallons
Lifespan
3-6 years
Origin
South America
Diet
Herbivore/aufwuchs grazer - algae, biofilm, blanched vegetables; supplement with algae wafers and sinking foods
Water Parameters
22-26°C
6-7.5
5-19 dGH
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Calculate heater sizeCare Notes
- Keep Otocinclus affinis in a mature, well-established freshwater tank (ideally 60+ liters / 15+ gallons) with lots of live plants, driftwood, smooth surfaces for biofilm growth, and gentle flow with high oxygenation.
- Maintain very clean, stable water: 22-26°C (72-79°F), pH ~6.0-7.5, soft to moderately hard water, and keep ammonia/nitrite at 0 with nitrates preferably <20 ppm; avoid sudden parameter swings and do regular small water changes.
- Do not rely on them to "live off algae"-feed daily with algae wafers, blanched zucchini/green beans/spinach, and occasional protein (e.g., small amounts of Repashy Soilent Green or similar) while ensuring food reaches them in community tanks.
- They are schooling fish and should be kept in groups of at least 6 (more is better) to reduce stress and improve feeding behavior; solitary otos often fade, hide, and lose weight.
- Choose peaceful tank mates (small tetras, rasboras, Corydoras, dwarf shrimp-friendly communities) and avoid aggressive or boisterous fish and fin-nippers; also avoid housing with large plecos that outcompete them for grazing spots.
- Acclimate slowly (drip acclimation recommended) and quarantine if possible, as otos are commonly stressed from shipping and may arrive underfed; prioritize individuals with round bellies, active grazing, and no sunken abdomen.
- Watch for starvation and wasting (sunken belly, lethargy), rapid breathing from low oxygen/high toxins, and sensitivity to medications (especially copper); treat cautiously and improve water/feeding before reaching for harsh meds.
- Breeding is possible in well-fed groups with excellent water quality: females lay small eggs on leaves/glass after cooler-water changes can trigger spawning, but adults may eat eggs and fry require infusoria/biofilm and very clean, stable conditions.
Compatibility
Good Tankmates
- Small, peaceful schooling fish (e.g., ember/neon tetras, harlequin/chili rasboras) that won't harass bottom-dwellers
- Peaceful livebearers in stable, mature tanks (e.g., guppies, platies) where food competition is managed
- Gentle bottom-dwellers (e.g., Corydoras species, small Kuhli loaches) that won't outcompete them for food
- Calm dwarf shrimp and snails (e.g., Amano shrimp, Neocaridina in well-planted tanks, nerite snails) as non-threatening cleanup crew
- Non-aggressive dwarf gourami relatives (e.g., honey gourami) and other mild-mannered community fish that ignore otos
Avoid
- Aggressive or boisterous cichlids (e.g., Oscars, convicts, large Central/South American cichlids) that may chase, injure, or eat them
- Large predatory fish (e.g., arowanas, large catfish, big barbs) that can swallow or relentlessly stress small otocinclus
- Fin-nippers and hyperactive species (e.g., tiger barbs, some larger danios) that can harass and outcompete otos at feeding time
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