CATFISH OTOCINLUS 3.5cm

Otocinclus (often called “Otos” or dwarf suckermouth catfish) are small, peaceful algae-eating catfish from the Loricariidae family.

They are popular in aquariums for their ability to graze on algae, especially in planted tanks. Otocinclus are native to South America.

They inhabit slow-to-moderately flowing rivers, streams, creeks, and flooded areas with plenty of vegetation, rocks, driftwood, and algae-covered surfaces.

They often gather in groups under floating plants or along vegetated banks in soft, well-oxygenated water.

They need space to graze and swim.

They are sensitive to copper medications and poor water quality—many losses happen shortly after purchase due to stress or ammonia spikes.

TANK SET UP: Minimum Tank Size 40-80 litres, ideally 80 litres for a group. Heavily planted tanks or added surface agitation (air stones) help with oxygen levels. Provide plenty of algae-covered surfaces, live plants (especially broad-leaved like Java fern), driftwood, smooth rocks, and hiding spots. A sandy or fine-gravel substrate works well.

They require mature, cycled tanks with established beneficial bacteria. Do not add them to new setups.

Monitor closely for the first few weeks after introduction— as they can be delicate during acclimation.

TANK MATE: Peaceful tankmates only (e.g., small tetras, Corydoras, shrimp).

MAINTENANCE: Perform weekly water changes of 25–50% (or at least 10–20% weekly). Ammonia and nitrite must be 0 ppm. Nitrates ideally under 20 ppm.

FILTRATION: Use a mature, well-established filter rated for at least 4x tank volume turnover per hour (e.g., strong HOB or canister filter) to maintain excellent water quality. They need good oxygenation but low-to-moderate water flow—avoid strong currents, which can stress them.

FEEDING/DIET: Primarily algae grazers (soft green algae, diatoms). Supplement with algae wafers, blanched vegetables (zucchini, cucumber, spinach), and sinking foods if natural algae are insufficient. They may starve in overly clean tanks.

NOTE: Most common species in the hobby, like Otocinclus macrospilus or O. vittatus, are not the same species, though they are closely related, often confused, and commonly mixed in the aquarium trade. They can be distinguished by the markings on their tails and the pattern of their lateral