Otocinclus vittatus

Today we take a closer look at the Otocinclus affinis. This peaceful and beautiful looking loricariid catfish is also known as an algae wonder weapon or mini fish and is especially popular in the community tank. If you have problems with algae but no aggressive fish in your tank, the ear-grid loricariid catfish is a real enrichment for you. Today, as always, we look at all the details in the profile and also in the attitude and also answer frequent questions. If you want to know more, you are welcome to leave a question as comment.

Otocinclus affinis profile

Scientific name: Otocinclus affinis
German name: Earflap Loricariid, Earflap Loricariid
Further designation: Mini fish
Origin: Brazil – Rio de Janeiro (South America)
Age: up to 5 years
Size: 4 – 5 cm (females longer and wider)
pH value: 6 – 7,8
Water: clear and oxygen-rich – with current
Water hardness: 2 – 20° dGH
Temperature: 20 – 27° C
Behavior: peaceful
Posture: Society, Group
Nutrition: Algae, green food tablets
Aquarium size: small to large (from 60 cm)
Facility: dense planting (broad-leaved plants)
Ground: sandy, fine gravel
Swimming zone: Bottom to middle area / disc
Family: Loricariid Catfish (Loricariidae)o
Order: Catfish (Siluriformes)
Subordination: Loricaroidei
Activity: active by day and night
Reproduction: Spawning on plant leaves
Breeding: medium to difficult (real affinis)
Price: 3-4 Euro

Otocinclus affinis Origin, appearance and characteristics

Otocinclus affinis
Marrabbio2, Otocinclus affinis, CC BY-SA 3.0

In nature, Otocinclus affinis lives in fast waters with many plants and algae. The popular minifish has its origin in Brazil, although it can be found throughout the Amazon region from Colombia to Paraguay. It was first introduced in Germany in 1920. The small loricariid catfish is intestinal breather, because in its home waters there is sometimes not enough oxygen in the water. It is found in white water and in black water. It is easiest to distinguish the males and females by size and build. When the otos are fully grown the female is a few millimetres longer and has a thicker belly. Usually the males are around 4 cm and the females around 5 cm tall.

Otocinclus affinis attitude

Even though it is often sold like this, the Otocinclus affinis is not really a beginner fish. We will explain below that it is not usually the Otocinclus affinis, although one would like to buy it. It is very important, no matter which Oto you have bought, that the tank has been running for a while and the Otocinclus affinis is not a first stocking. The planting should already have grown strongly and ideally there should be plenty of algae for the little Oto. The Otocinclus affinis can be very sensitive to stress and whether it will survive being planted in its new habitat can only be determined after 2 weeks. Apart from the right water values and a natural food supply, society is also a decisive factor.

Behavior and socialization

The Otocinclus affinis is very sociable, but does not necessarily need a community aquarium – much more important is that it has a group of the same species. The group keeping starts from 6 specimens, but it is not wrong to keep much more. The larger the group, the more vital the small fish are. During socialization it gets along very well with other peaceful creatures. Especially suitable are shrimps, armoured catfish and characins. One can only advise against socializing with aggressive fish species.


The temperature indication is not so easy, because in many cases in the trade it is not really the Otocinclus affinis. Therefore, the data of the traders and also of the different sources fluctuate. Usual temperature data are 20 – 26° C or 23 – 27° C.


If the fish is sold as cleaner fish or exclusively algae-eating fish, you should be very wary, because this is not true. Certainly the Otocinclus affinis is a real secret weapon against all kinds of algae in the aquarium, but a varied diet offers more than just algae. Small live or frozen food like Cyclops or Daphnia are a welcome change. In nature, algae inevitably contain many micro-organisms which are also destroyed. If you do not have enough algae in your aquarium, you can remedy this with green food tablets.

It should be said here, however, that the fish are wild-caught and know only the food intake of the algae, especially in the beginning. This means that if there are no algae in the aquarium and you feed them with tablets, it can happen that they will not be accepted. Especially green algae on the bottom gravel are very fond of Otocinclus affinis. It loves to graze the substrate. But you should not buy these beautiful miniature fish exclusively for algae control, this is the same solution as loaches for snails. You reduce the amount, but you do not solve the problem.

Aquarium size

With the Otocinclus affinis you don’t need to take into account a lot of space for the aquarium size. Some dealers say that one tank from 40 or 60 cm would be sufficient. I find 80 cm to be a good entry-level tank.

Furnishings and plants

A pool with a strong structure through many plants, stones and roots is very important for the well-being. Above all, however, the substrate is decisive: here it is best to use sand or fine gravel. In general every plant is grazed by Otocinclus affinis, but broad-leaved plants (for example Echinodorus bleheri) are often used as resting place. Especially in the beginning hiding places are often used.

Water values

As with temperature, the different sources also differ in water values. According to my opinion and examination of some sources, the ideal value for water hardness should be between 2 – 20 ° dGH and the pH-value should be 6-7.5. The water should be oxygen-rich and very clear. If one notices that the Otocinclus affinis comes to the water surface too often to absorb oxygen, this could be a signal that there is not enough of it in the water and a water change is due.

Otocinclus affinis breeding

The miniature fish sold as Otocinclus affinis in specialist aquarium shops can usually be bred quite easily. If it is the real Otocinclus affinis then this is usually much more difficult. Here you are usually lucky if a female was already fertilized during transport. But unfortunately one is not sure whether this is a offspring of Otocinclus affinis in particular. In the countries of origin the fish are usually not kept pure and so it is difficult to tell which Otocinclus it is.

The eggs are laid on the leaves of plants, where they hatch about three days later. The offspring can then be fed with powdered food.

Buy Otocinclus affinis

When bought in shops, the Otocinclus affinis is usually around two centimeters in size. Even if the catfish are sold with the name Otocinclus affinis you cannot be sure that it is really this one. In most cases they are related animals like:

  • hopei
  • huaorani
  • mariae
  • macrospilus
  • vittatus
  • vestitus
]The Otocinclus affinis meanwhile belongs to the genus Macrotocinclus.

When buying it you should take care that the fish look vital and do not have collapsed bellies. The catfish should not be at the dealer's for too long, but if possible they should have acclimatized in the tank for two weeks (see above).


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