Hot Water Fish


  • Scientific name: Otocinclus Affinis
  • Common name: Otocinclo Dorado, Glass Cleaning fish, Otocinclo dwarf, Otocinclus dwarf, Otocinclus dorado
  • Aquarium size: 60 liters
  • Temperament: Calm
  • Temperature: 21ºC to 26ºC
  • pH: 5.5 to 7.5
  • Diet: Mainly vegetarian
  • Length: 4 to 5 centimeters


The Otocinclus affinis or Golden Otocinclo , is a very small loricarid , which in the aquarium hobby is highly valued for its ability to clean the aquarium (clean glass) , since its main food is algae.
It also stands out for its peaceful attitude, which allows it to be kept in a community aquarium, where it shares space with other fish that are not too active.


These fish can measure between 4 and 5 centimeters in length, are elongated in shape, rounded on the back and flattened ventrally.

Its head is slightly flattened, with the eyes located on both sides, which gives it a
side view.

One of the most original morphological characteristics, although typical of Loricars, is
the presence of a suction cup in the mouth, which serves both to feed and to fixate on rocks or plants, very useful in their natural habitat of rivers with strong currents.

They are fish lacking a swim bladder, which prevents them from swimming.
To solve it, they make lateral jumps and hold onto the substrate with their mouths, to avoid being swept away by the current of the rivers they inhabit.

The fins have reinforcing spines , similar (although not so strong) to those of the Hypostomus plecostomus , with which it shares the nickname of Pool Cleaner or Glass Cleaner.

It does not have spines on the adipose fin and the tail fin.

As for the
differences between male and female (sexual dimorphism) , they are almost negligible. Perhaps the female is somewhat rounder and larger, while the male is more slender and somewhat smaller.


They are fish of ocher yellow color to gold, with black lateral stripes that run throughout their body, from the tail fin to the mouth. This strip narrows as it reaches the tail fin, where it ends with a spot-shaped spot.
The back is dark brown with black specks and golden reflections, it also covers the entire fish. The ventral part is white.

Distribution and habitat

They originate from the southeast of Brazil, in the Mato Grosso jungle and it is also possible to find them in some rivers of Colombia: Río Caquetá, Canca and Japurá.

They like
clear waters with strong currents, where they find their favorite food in the rocks covered with algae and the abundant vegetation.

Aquarium conditions

They are gregarious fish, it is recommended to have a small group in the aquarium of between 4 and 6 specimens, which will be comfortable in a tank with a size of about 60 liters.
The water temperature must be between 21ºC and 26ºC, with special attention to the higher temperature, since they are not fish that endure excessively high temperatures.

Regarding the quality of the water, it
is recommended to maintain a pH of between 5.5 to 7.5 with a hardness from soft to semi-soft, typical of its place of origin.

The community aquarium should recreate an Amazon biotope, with
a good number of broadleaf aquarium plants ,that facilitate the growth of algae, and that also provide shelter, since they are quite shy and are not very good swimmers.

Due to their special type of diet, almost exclusively algae,
it is not recommended to introduce them into a new aquarium, where they would not find enough food to survive.

The quality of the water has to be optimal, in its natural habitat the waters are very clean and oxygenated.
They are «algae eaters», they are not «bottom cleaner» fish and therefore
do not support an accumulation of nitrites.

Continuing with the aquarium conditioning, a filter should be included that causes a good movement of the water, with the precaution of protecting the filter inlet, so that the fish (small size) are not absorbed.


They are mainly herbivorous fish, consuming mostly green and brown algae, small plants and microorganisms present in the plants.

In the aquarium they
can also accept cooked vegetables: zucchini, peas and lettuce, as well as artificial food and tubifex.

Some aquarists also provide protein foods, especially insect larvae.

They must be provided with a trunk or root, from which they provide cellulose.

Behavior and compatibility

The Otocinclus affinis species of twilight habits. During the day it can remain hidden or fixed in the glass, on a plant or any decoration in the aquarium. At night it will come out and feed.

They are also gregarious,
preferring to stay in a small group, which should ideally be at least about 5 specimens (with a higher proportion of females than males), although it may be higher depending on the aquarium.
Peaceful and shy, the plants will serve as a hiding place.

They can share the space with other species in the aquarium, taking care to
look for companions that are not too large and active.

It is recommended
not to mix Otocinclus affinis, with Discus fish , since these shed a mucosa, which is very attractive for the Otocinclus and stick to their sides, being annoying and stressful for the Disks.


Reproduction of Otocinclus affinis is difficult, although it seems not impossible.

To encourage spawning, despite being especially vegetarian fish,
they should be fed live or frozen food.

It is also possible to
promote spawning, with partial and continuous changes in the water, simulating the rainy season of its origin.

The group must be made up of more females than males, who will chase them until they are accepted.

Once achieved
, the females lay their eggs (between 20 and 40 per specimen) on the walls of the aquarium or on the leaves of the plants.

The clutches are not very abundant, and the parents abandon their eggs, which we can collect and transfer to a breeding aquarium.

Their hatching occurs after 2 or 3 days.
Small fry will be born, which can be fed the first days with infusoria, to gradually add to the diet, brine shrimp nauplii and boiled and highly crushed vegetables.

Photos of Otocinclus affinis

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