The Otocinclus catfish (commonly called "Oto") is a small, peaceful freshwater fish famous for being one of the most effective algae eaters in the aquarium hobby. Native to South America, these "dwarf suckermouths" are prized for their ability to meticulously clean algae from plant leaves, glass, and decorations without damaging them. Core Care Requirements Tank Size: Minimum 10 gallons, though 20 gallons or more is better for maintaining stable water parameters and providing enough grazing surface. Social Needs: They are schooling fish and should be kept in groups of at least 6 or more to feel secure and display natural behavior. Diet: Primarily herbivores. They specialize in soft green algae and brown diatoms. Since most tanks cannot produce enough algae to sustain a school, you must supplement their diet with: High-quality algae wafers or spirulina pellets. Blanched vegetables like zucchini, cucumber, or spinach. Pro Tip: Look for a "pearl-like" rounded belly; a sunken belly is a sign of starvation, a common cause of death in new Otos. Water Parameters (2026 Standards): Temperature: 72°F – 79°F (22°C – 26°C). pH: 6.0 – 7.5 (slightly acidic to neutral). Cleanliness: They are highly sensitive to nitrates, ammonia, and nitrites. Weekly water changes of 25–30% are essential. Key Challenges Acclimation Sensitivity: Otos are notorious for being delicate during the first month. They are often wild-caught and arrive at stores stressed and underfed. Drip acclimation is highly recommended to prevent shock from parameter changes. Established Tanks Only: Never add Otos to a brand-new, uncycled aquarium. They require an established environment with existing biofilm and algae to survive their first few weeks. Ideal Tank Mates Because they are entirely peaceful, they are perfect for community tanks with other non-aggressive species: Fish: Tetras, rasboras, guppies, and Corydoras catfish. Invertebrates: Cherry shrimp, Amano shrimp, and various snails. Avoid: Large or aggressive fish (like Oscars or large Cichlids) that might see them as food
