Giant otocinclus

Hypoptopoma psilogaster

Also known as Psilogaster oto

FreshwaterFish

Giant otocinclus (Hypoptopoma psilogaster) — The Wet Spot Tropical Fish · Used with permission

Care at a glance

Temperature: 75–82°F (24–28°C)
pH: 6.0–7.5
Adult size: 3.1 in (8 cm)
Minimum tank: 29 gal (110 L)
Temperament: Peaceful
Social behavior: Social
Swim level: Bottom
Difficulty: Medium
Breeding: Medium
Rarity: Rare
Origin: Upper Amazon, Peru
Family: Loricariidae

Overview

This is an oversized oto, and like the small ones it is a social grazer that does best in a group of several rather than alone, so buy a handful and let them work the tank together. They are gentle, peaceful fish that spend the day clinging to wood, broad leaves, and glass, scraping algae and biofilm. Keep them only with calm tankmates that will not outcompete them at feeding time. The single most important thing is a mature tank with real algae and biofilm to graze; back that up with algae wafers and blanched vegetables such as zucchini. A tank of about 110 liters suits a small group.

In the wild

It lives in the upper Amazon of Peru, in warm, clear, oxygen-rich water among plants, wood, and submerged roots. Aim for gentle to moderate flow, clean soft water, and lots of surfaces for algae to grow, using driftwood, rounded stones, and hardy plants. Warm water around 24 to 28 C with a pH of 6.0 to 7.5 fits it, and frequent water changes keep the low-waste conditions these grazers need.

Good to know

Hypoptopoma psilogaster is a member of the Loricariidae and reaches around 8 centimeters, large for an oto but still a slim, flat-bodied grazer. Its eyes sit low and to the sides of a flattened head, a feature shared across the whole genus. It is an egg layer of moderate breeding difficulty that fixes its eggs to firm surfaces.

Did you know

Its eyes are set so low on the sides of its head that it can see underneath its own body while it is stuck to the top of a leaf or branch, keeping watch below even as it grazes above.