OtocinclusOtocinclus (Otocinclus sp.) is one of the most useful and charming small fish available for the planted aquarium. These compact, armored catfish spend virtually every waking moment rasping algae from glass, plants, and hardscape — making them one of the most effective natural algae control solutions available. Despite being listed as Otocinclus affinis in much of the older aquarium literature, the fish actually available in the trade belong to several closely related species including O. vittatus, O. vestitus, and O. macrospilus. All share identical care requirements and the same tireless algae-eating habits.Feeding & Care Tip: Live algae growing on the aquarium glass, plants, and hardscape is the single most important food source for Otocinclus — a tank without established algae growth will not sustain these fish regardless of what supplemental food is offered. Allow biofilm and green algae to develop on surfaces before adding otos, and do not over-clean the aquarium. Supplement with Hikari Mini Algae Wafers placed directly on the glass or substrate, and offer blanched vegetables — zucchini, cucumber, or spinach — 2–3 times per week. Remove uneaten vegetable matter within 24 hours to prevent water quality issues.Native to slow-moving rivers and streams across a wide range of South America — from Venezuela south through Brazil, Peru, Bolivia, and Argentina. Trade specimens are almost exclusively wild-caught, typically from Peru, Colombia, or Brazil. They inhabit clean, well-oxygenated, slightly acidic to neutral water with abundant aquatic vegetation and algae-covered surfaces.Otocinclus are schooling fish that are markedly more confident, active, and healthy in groups. A lone otocinclus is a stressed otocinclus — it will hide constantly, refuse supplemental food, and decline over time. Keep a minimum of six, and ideally eight or more. In a proper group they are bold, constantly grazing, and frequently seen resting together in clusters on broad plant leaves or the aquarium glass.Otocinclus are notoriously sensitive during the transition from the wild to captivity — virtually all trade specimens are wild-caught, and the stress of collection and shipping leaves them vulnerable in the first weeks. Slow, careful drip acclimation over at least an hour is strongly recommended. A mature aquarium with established algae growth, stable water parameters, clean water, and good oxygenation gives newly arrived fish the best possible start.Care & Ideal Parameters Difficulty Easy — Moderate Temperament Peaceful — Community Typical Adult Size 1.5 inches (3.8 cm) Min. Group Size 6 minimum — groups of 8+ strongly recommended Ideal Temp 72–79°F (22–26°C) Ideal pH 6.0–7.5 Ideal GH 2–15 dGH Ideal KH 1–8 dKH Primary Food Live algae and biofilm (from aquarium surfaces); Hikari Mini Algae Wafers Supplemental Food Blanched zucchini, cucumber, or spinach — offered 2–3 times per week Origin Widely distributed across South America Notes Wild-caught — sensitive during acclimation. Established algae essential before adding. True O. affinis is rare in trade — most fish are O. vittatus, vestitus, or macrospilus. Do not add to a new or algae-free tank. Groups of 6+ essential.
