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Side profile of an "Oto" catfish. The Oto is attached to the glass wall using it's mouth.
Belly view of an Oto catfish.
A group of Oto catfish on the glass in an aquarium.
The dorsal view of an Oto catfish.

Otocinclus Catfish

Menagerie Live Fish
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Tank Level:


Minimum Tank Size:

10 Gallons





General water hardness:

5-15 dGH


72 F to 82 F                      




Oto Cats (Otocinclus sp.) are a small, energetic algae-eating suckerfish. They are narrow-bodied, with a black stripe doing down the length of their bodies. These animals are frequently bought as a tiny and peaceful alternative to pleco species. 

These little fish stay under 2 inches in length, making them a great option for nano tanks. A shoal of 6 otocinclus catfish can live comfortably in a 10-gallon aquarium. While a few can be kept in a 5-gallon aquarium, they are less shy in larger shoals. They are most comfortable in temperatures in the mid-70's. 

While these animals relatively easy and undemanding to keep, they are very sensitive to poor water quality and water quality fluctuations. Only add them to aquariums that are fully cycled. It is recommended to drip-acclimate them to your aquarium when you receive them.

Otocinclus catfish are herbivores. They will eat algae off of most surfaces in your aquarium, such as the walls, gravel, decorations, and live plants. They can also eat blanched vegetables like zucchini. It is very easy to underestimate how much algae they need; sometimes owners will accidentally starve their Oto catfish because they rely purely on the algae growing in the aquarium. Their diet should be supplemented daily with algae rounds, kelp flakes/pellets, and blanched vegetables, in addition to the algae that naturally grows in your aquarium.

These animals are extremely peaceful and don't really have a method of self-defense. They should be kept exclusively with peaceful community fish and bottom-feeders that will not act aggressively towards the oto catfish.