Dwarf Oto (Macrotocinclus affinis)

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Otocinclus affinis.jpg
Dwarf Oto

Macrotocinclus affinis

38 Litres (10 US G.)

3.8-5.1cm (1.5-2 ")




6.0 - 8.0

20 -26 °C (68-78.8°F)

15-20 °d

1:2 M:F

Pellet Foods
Other (See article)

4-5 years



Additional names

Oto, Dwarf Otocinclus, Golden Otocinclus, Dwarf Otto, Dwarf or Midget Suckermouth Catfish.

Additional scientific names

Otocinclus affinis


From the freshwater Orinoco river system in the Amazon river


Difficult. Females are slightly bigger than males.

Tank compatibility

A peaceful community fish. Will co-habit with other peaceful tank mates.


Otos will mainly graze on some soft algaes, primarily diatoms, and blanched vegetables such as Zucchini (Courgette), Carrot, Potato and Cucumber. They may also accept some algae wafers, but it can take some time to wean them onto these. They will not eat hair algae or green spot algae.

Feeding regime

They graze on algae virtually all the time, so ensure they get enough.

Environment Specifics

A planted aquarium is a must. Ensure you get them in decent numbers, 3 or more is good. 6 or more is far better. They are a nervous fish if not kept in groups (in the wild they school in groups of several thousands) and have been know to die from stress if kept alone. As this small fish eats whilst resting on a surface, they are easy targets for larger fish in the wild.


They tend to rest on any object, including the front glass so you'll get plenty of views of their underside. Prefers to keep near its own company. Will occasionally be seen sleeping, and can awake and dash about if startled.


Very pale body band with almost a golden sheen to it. See picture.
This species is often incorrectly identified. But is hard to find in the trade.
Most web sites incorrectly label Otocinclus macrospilus as this species.

Special note[edit]

These peaceful community fish are often starving when you see them in the average pet shop and consequently they have a reputation of having a high mortality rate within the first month of ownership.
Ensure that you look at their bellies carefully in the shop and if they look very thin or hollow bellied then tell the shop to feed them more algae tablets. These fish need to eat all the time.
When you get them home, let them settle into a quiet tank and put in plenty of algae tablets for them to chew on. The first week is fairly critical.
Many websites/aquatic stores incorrectly label Otocinclus macrospilus as this species.


External links[edit]