Dwarf oto

Adults reach about 3.5 cm in length. Sexual dimorphism is weak; females are only slightly larger (wider) than males, visible when viewed from above. The mouth is shaped like a sucker, allowing the fish to scrape algae efficiently from various surfaces such as stones or leaves. The body is grey with a broad dark stripe running along the entire length from head to tail. The belly remains white.

The dwarf oto is naturally found in South America, mainly in the upper Amazon region of Peru. A wider range that also includes Colombia and Ecuador is sometimes mentioned. It lives in streams and small rivers where aquatic plants grow abundantly. These areas often have floating meadows formed by numerous plants on the water surface, which serve as shelter for various fish species, including this oto.

The dwarf oto is a peaceful, calm fish that prefers to live in small groups. It gets along well with other non-aggressive species of comparable size, such as Corydoras catfish, small tetras, or American cichlids. Do not keep them with overly active fish.

A pair needs a tank of at least 40 litres. The aquascape should include plenty of plants—both rooted and floating, with broad or narrow leaves. Also provide driftwood and other hiding places. Natural bogwood can serve as a substrate for algae growth, providing an additional food source. The choice of substrate is not critical, since the dwarf oto spends most of its time above the substrate, on plant leaves. High water quality and appropriate water parameters are essential for keeping them. A good filtration system is desirable; choose one that does not create excessive flow. Weekly water changes and regular removal of organic waste are mandatory.

In the wild, as noted, this fish feeds on algae and small insects and crustaceans living in it. In a home tank, the diet should be primarily plant-based. Examples include pieces of cucumber, spinach, zucchini, or spirulina flakes. Live or frozen foods such as bloodworm, brine shrimp, or daphnia may be given occasionally.

Breeding this species is possible but may be difficult for beginners. Raising fry is often problematic. Reproduction is similar to Corydoras, but unlike them, the eggs are scattered randomly.

Most illnesses in this fish result from poor conditions and inadequate nutrition. If you notice early symptoms, first check the water parameters and concentrations of dangerous substances such as ammonia, nitrites, and nitrates. If the readings are off, correct them before attempting any treatment.

When buying dwarf otos, prefer individuals that have been quarantined and acclimated in the shop, as most wild-caught fish struggle with a change of conditions. Examine the fish carefully: a healthy dwarf oto should be active, with no visible damage, spots, or signs of emaciation. A rounded belly is the main sign that the fish is healthy and getting enough food. Avoid fish with a sunken belly, rapid breathing, or sluggish behaviour, as these often indicate stress, disease, or severe food shortage. If possible, check whether the fish will accept prepared foods to make future care easier.