Otocinclus Care Guide
Otocinclus (otos) are tiny, peaceful algae-eating catfish beloved by planted tank keepers. They're delicate but rewarding, gentle on plants, tireless workers, and endlessly entertaining to watch as they graze across every surface.
Quick Facts
High Mortality Warning
Otocinclus have notoriously high mortality rates in the first few weeks after purchase. Most are wild-caught and stressed from shipping. Drip acclimate for 2-3 hours, quarantine new fish, and only add them to mature tanks with established algae growth. Never buy otos from a tank where others look sickly or dead.
Tank Requirements
Ideal Setup
- Tank size: 20+ gallons for a group of 6
- Plants: Heavily planted tanks provide grazing surfaces and security
- Mature tank: Only add otos to tanks that have been running 3+ months with established biofilm
- Flow: Gentle to moderate, they don't like strong currents
- Substrate: Sand or smooth gravel (they rest on the bottom)
- Driftwood: Provides surfaces for biofilm growth and hiding spots
Perfect for Planted Tanks
Unlike many plecos, otos are completely plant-safe. They only eat algae and biofilm, never plant tissue. They're the ideal algae crew for delicate aquascapes.
Ideal Water Parameters
Diet & Feeding
Otocinclus are specialized herbivores that primarily eat soft green algae and biofilm. Starvation is the #1 killer of otos, most tanks don't have enough natural algae to sustain them long-term.
What They Eat
- Primary: Soft green algae, diatoms (brown algae), biofilm
- Supplements: Blanched zucchini, cucumber, spinach
- Prepared foods: Algae wafers, Repashy Soilent Green, spirulina wafers
- Won't eat: Hair algae, black beard algae, green spot algae (too tough)
Supplemental Feeding is Essential
Even in algae-rich tanks, supplement with blanched vegetables 2-3x per week. Watch for sunken bellies, a sign of starvation. Healthy otos have rounded, full bellies.
Tank Mate Compatibility
Otos are extremely peaceful and timid. They do best with calm, non-aggressive tank mates that won't outcompete them for food or stress them.
Common Problems & Solutions
Starvation
Sunken belly, visible spine, lethargic behavior, pale coloration
Tank is too clean, not enough algae/biofilm, competition for food
Supplement with blanched veggies, algae wafers, Repashy gel food
Acclimation Shock
Wild-caught otos are very sensitive. Deaths within 48 hours are usually acclimation failure.
Prevention: Drip acclimate 2-3 hours minimum
Poor Water Quality
Otos are sensitive to ammonia and nitrite. Only add them to cycled, mature tanks.
Prevention: Tank cycled 3+ months, 0 ammonia/nitrite
Quick Tips
- Keep at least 6 otos, they're social and feel safer in groups
- Only add otos to mature tanks (3+ months) with established biofilm
- Drip acclimate for 2-3 hours, never rush this step
- Supplement diet with blanched zucchini even if you see algae
- A healthy oto has a rounded belly, sunken belly = starving
- They're nocturnal, you'll see more activity at night or when lights are low
- Avoid buying otos that look thin or are in tanks with dead/dying fish
- They won't eat hair algae, BBA, or green spot algae, only soft green algae
Frequently Asked Questions
Why do my otocinclus keep dying?
Most oto deaths are from starvation or acclimation shock. They need mature tanks with established algae/biofilm, supplemental vegetables, and slow drip acclimation when introduced. Wild-caught otos are fragile, only buy healthy-looking fish from reputable sources.
How many otocinclus should I keep?
At least 6. Otos are social and feel more secure in groups. A single oto will hide constantly and stress out. In larger tanks (40+ gallons), groups of 10-12 are ideal and you'll see more natural behavior.
Will otocinclus clean my tank?
Otos eat soft green algae and diatoms (brown algae), but they won't touch hair algae, black beard algae, or green spot algae. They're excellent for planted tanks but shouldn't be your only algae control strategy.
What should I feed otocinclus?
Primary diet is algae and biofilm. Supplement with blanched zucchini or cucumber, algae wafers, and Repashy Soilent Green. Even in algae-rich tanks, supplemental feeding 2-3x weekly helps ensure they don't starve.
Related Resources
Track Your Otos' Health
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