Otocinclus Catfish – Otocinclus spp.

Otocinclus catfish are among the most beloved freshwater fish for planted aquariums and peaceful community tanks. Small, gentle and extremely efficient at cleaning soft algae, these charming fish have earned a permanent place in the hearts of aquarists around the world. In this article we explore their natural behaviour, specific care requirements, ideal tank setups and compatibility with other species, so that you can enjoy healthy and active Otocinclus in your home aquarium. At MB Store you will also find a wide selection of aquariums, filtration systems and accessories to create the perfect environment for these unique algae eaters.

Natural habitat and behaviour of Otocinclus

Otocinclus catfish (Otocinclus spp.) come from South America, where they inhabit slow-flowing tributaries of large rivers such as the Amazon, Paraná and Orinoco. In the wild they usually live in shallow, well-lit waters rich in aquatic plants and submerged roots. The substrate is often sandy or muddy, covered with a thin layer of biofilm and soft algae, which form the basis of their diet.

These fish are small, usually reaching between 3 and 5 cm in length depending on the species. Their body is elongated, slightly flattened on the underside, perfectly adapted to clinging to leaves, roots and glass. Thanks to a strong sucker-like mouth, they can rasp off algae from flat surfaces without difficulty, even in places with moderate current.

Otocinclus are social animals that feel safest in groups. In nature they often form loose shoals, moving together along leaves and stones while feeding. In the aquarium this behaviour is repeated: a group of six or more individuals will constantly graze on surfaces, occasionally darting to the surface for air. Their peaceful nature and small size make them excellent inhabitants for planted community tanks, provided that their specialised needs are met.

Understanding their natural environment is crucial, because Otocinclus are not as adaptable as many popular aquarium fish. They come from clean, oxygen‑rich waters with stable parameters, and this should be reflected in aquarium conditions. Sudden changes in temperature, pH or water chemistry can quickly weaken them. For this reason, careful planning of the tank and regular maintenance are essential if you want to keep them healthy for years.

Tank requirements and ideal conditions

Although Otocinclus are small, they must not be kept in unstable, tiny tanks. A practical minimum volume is around 45–60 litres for a group, but more space is always beneficial. The longer the tank, the more surfaces are available for algae growth and natural behaviour. MB Store offers aquariums in many sizes that allow you to choose a stable and aesthetically pleasing solution tailored to your home and the number of fish you plan to keep.

Water parameters should be as close as possible to those in their natural environment. Otocinclus feel best at a temperature of 22–26°C, with a pH between 6.0 and 7.5 and soft to moderately hard water. The most important factor, however, is stability. Frequent, abrupt changes in temperature or pH are much more dangerous than minor deviations from the ideal range. Regular water changes of 20–30% per week help keep nitrates low and maintain a clean, oxygenated habitat.

Filtration must ensure high water quality and good oxygenation, but the current should not be too strong in the entire tank. A filter that creates gentle movement at the surface and along the front glass is usually sufficient. In MB Store you can find internal, external and hang‑on filters, as well as suitable filter media that support efficient biological filtration. Be sure to cover inlets with pre‑filters or fine sponges to protect delicate fish from being sucked in, especially juveniles.

Lighting plays a dual role. On one hand it supports plant growth, on the other it encourages natural algae formation, which is essential for Otocinclus. Moderately strong light with a daily cycle of 7–9 hours is a good starting point. Too long a photoperiod can cause uncontrolled algae outbreaks in the entire tank, but a total lack of light will deprive these fish of one of their most natural food sources. Balance between plant needs, algae control and the comfort of other inhabitants is key.

Stability also involves avoiding sudden cleaning of all surfaces at once. Otocinclus rely on a steady supply of soft algae and biofilm; if everything is cleaned to a sterile shine in one day, they may suffer from food shortage. It is better to clean the glass in sections and leave some surfaces for them to graze on. The goal is a clean, yet biologically rich environment rather than an absolutely spotless one.

Aquascaping and decoration for Otocinclus

Designing a tank for Otocinclus is an ideal opportunity to create a nature‑inspired aquascape. These fish look most impressive in densely planted aquariums, where they can move freely among leaves, roots and stones. Live plants are almost indispensable: they not only absorb excess nutrients and stabilise the tank, but also provide additional surfaces for algae and biofilm growth. At MB Store you will find aquariums, dedicated lighting and substrates that support healthy plant development.

Foreground carpets made of small plants, midground compositions with stems and background groups of tall species create a three‑dimensional landscape full of hiding places. Otocinclus particularly like broad leaves of plants such as Anubias or Echinodorus, on which thin films of algae often develop. Clinging to such leaves, they feed in a very natural way, and the aquarist can observe their characteristic behaviour up close.

Hardscape elements such as roots and stones are also important. Driftwood not only decorates the tank, but can also foster the growth of microorganisms valuable in the diet of these fish. Stones with slightly rough surfaces provide additional feeding area. When arranging the decoration, it is worth leaving some open space for swimming, especially along the front glass, where Otocinclus often form small groups grazing together.

Substrate should be safe and gentle, especially if you plan to keep other bottom‑dwelling fish alongside. Fine sand or small rounded gravel works best. A darker substrate enhances the colours of fish and plants, giving the aquarium a more natural look. In the range of MB Store you can choose from various types of substrates, including specialised ones for planted aquariums, as well as decorative sands and gravels suited to different styles of aquascaping.

Additional decorations, such as small caves or ceramic tubes, can be useful as extra hiding places, although Otocinclus themselves rarely use deep shelters. However, they appreciate calm zones among dense vegetation, where they can rest between feeding sessions. The entire composition should be arranged so that there are no sharp edges and narrow gaps where a small fish could get stuck.

Diet and feeding strategies

The reputation of Otocinclus as exceptional algae eaters is fully justified, but relying solely on algae in the aquarium is a common mistake. In many home tanks natural algal growth is insufficient to meet their nutritional needs, especially shortly after setting up a new aquarium. Therefore, it is essential to offer them a diverse and well‑planned diet that replicates the composition of their natural food as closely as possible.

In the wild these fish feed mainly on soft green algae, biofilm and microorganisms living on plant leaves and submerged surfaces. In the aquarium they willingly graze on soft algae on glass, leaves and decorations, but thick and hard deposits are usually ignored. To supplement their diet, you should regularly provide them with high‑quality sinking foods designed for algae eaters. Look for tablets or wafers rich in spirulina, vegetable matter and balanced plant proteins.

Blanched vegetables are an excellent addition to their menu. Slices of zucchini, cucumber, spinach or peas can be briefly blanched and then placed in the tank using special clips. After feeding, any leftovers should be removed after several hours to avoid pollution. Observing how Otocinclus gather on such a vegetable “plate” is not only practical, but also very entertaining.

Some aquarists worry that additional feeding will make these fish lazy and reduce their algae‑eating activity. In reality, a well‑fed Otocinclus is more active, has a stronger immune system and lives longer. Hunger and malnutrition lead to weakening, increased susceptibility to disease and a higher mortality rate, particularly in newly purchased individuals. A balanced diet ensures the right level of energy for constant grazing behaviour throughout the day.

Feeding frequency should be adapted to the number of fish and the amount of natural algae available in the tank. In a mature, well‑lit aquarium you can feed small portions once a day, monitoring how quickly the food disappears. In newer or very clean tanks daily supplementation with plant‑based foods is essential. Over time you will learn to read the behaviour and body condition of your Otocinclus and adjust the feeding schedule accordingly.

Social needs and suitable tankmates

Otocinclus are highly social fish and should never be kept singly or in pairs. A group of at least six individuals is recommended, and larger numbers are even better if the tank allows. In a shoal they feel much safer, show natural schooling behaviour and are less prone to stress. Stress reduction is especially important for this species, which is known for its sensitivity, particularly in the first weeks after introduction to a new aquarium.

Their temperament is peaceful and non‑aggressive. They neither nip fins nor compete aggressively for food. Thanks to this they make excellent residents of community aquariums, provided that tankmates are chosen carefully. Ideal companions include small tetras, rasboras, peaceful livebearers, dwarf cichlids with calm character and various small shrimps. Such a combination allows you to create a dynamic yet harmonious aquascape full of life.

What should definitely be avoided are large, predatory or hyperactive fish. Species such as big cichlids, barbs known for fin nipping, or aggressive bottom dwellers can stress or even injure Otocinclus. Also unsuitable are tanks focused on very strong current, like some specific river setups, where these small catfish would struggle to maintain their natural behaviour.

Coexistence with shrimps is usually very successful. Otocinclus do not hunt adult shrimps and show no interest in their offspring. In fact both groups benefit from similar water conditions and abundant vegetation. Snails are also good companions, complementing the cleaning crew and helping to manage leftover food. Such a balanced community supports a stable micro‑ecosystem, which in turn benefits the health of all inhabitants.

When planning a community tank, consider feeding strategies. Slowly sinking foods and vegetables should be distributed so that Otocinclus have access to them, rather than being quickly eaten by more assertive fish. It can be useful to feed the rest of the community on one side of the tank while placing wafers for Otocinclus on the other, giving them time to feed calmly.

Acclimation, health and common problems

One of the greatest challenges in keeping Otocinclus is the initial acclimation phase after purchase. These fish are often caught in the wild and may arrive at shops weakened, with depleted fat reserves. That is why choosing a reliable source is essential. When buying, observe whether fish have slightly rounded bellies, show active grazing behaviour and do not display rapid gill movement or visible damage to fins and skin.

Acclimation to the home aquarium should be slow and careful. A gradual drip method works best, allowing water from your tank to mix little by little with the shop water. This reduces stress caused by differences in temperature, pH and hardness. After introduction, keep lighting dim for a few hours and avoid sudden movements around the aquarium. A calm environment helps them adapt more quickly.

Health problems in Otocinclus often stem from poor water quality, unstable parameters or long‑term malnutrition. Symptoms such as lethargy, refusal to feed, hollow bellies or clamped fins should prompt immediate action. Regular testing of ammonia, nitrite and nitrate levels, along with consistent maintenance, is crucial. Even small amounts of ammonia or nitrite are dangerous, as these fish are particularly sensitive to toxins.

Preventive care involves not only clean water, but also a varied diet and avoiding aggressive tankmates. Quarantine for new fish entering the community tank is a valuable practice. It allows you to monitor newcomers for disease and reduces the risk of infection spreading. MB Store offers equipment that facilitates safe acclimation and quarantine, including smaller tanks, heaters and filters suitable for temporary setups.

Thanks to good care Otocinclus can live several years, becoming active and reliable members of the aquarium community. Their constant presence on leaves, glass and decorations makes the tank appear more natural and dynamic. Observing their behaviour is also an excellent lesson in understanding the functioning of a small aquatic ecosystem at home.

Breeding considerations in the home aquarium

Breeding Otocinclus in captivity is possible, but significantly more demanding than for many popular species. Most individuals available in the trade are still wild‑caught, which shows how challenging large‑scale breeding can be. Nevertheless, some experienced aquarists have achieved success, and analysing the conditions that favour spawning is valuable, even if your main goal is simply long‑term care.

First of all, a stable, mature aquarium is essential. Fish must feel completely safe and have constant access to high‑quality food before they will attempt to breed. A well‑planted tank with numerous leaves and gentle filtration provides the right foundation. Good water quality, soft to moderately hard water and slightly acidic to neutral pH are seen as positive factors for spawning attempts.

The spawning behaviour of Otocinclus resembles that of many other small catfish. Males pursue females, and spawning most often takes place on the underside of leaves or on the glass. Eggs are usually scattered in small clusters rather than laid in a nest. After spawning, parents do not provide care for the eggs, so they may be eaten by other inhabitants or even by the adult Otocinclus themselves.

If you want to increase the chance of raising fry, consider a separate breeding tank. You can transfer a group of well‑conditioned adults, wait for spawning and then return them to the main aquarium, leaving the eggs in the breeding tank. Gentle aeration near the eggs improves oxygenation and helps prevent fungal growth. After hatching, the fry initially feed on microscopic organisms and biofilm; later they accept finely crushed plant‑based foods and infusoria.

Even if you do not plan purposeful breeding, awareness of this process helps you interpret certain behaviours, such as intense chasing or unusual activity. It also highlights how important it is to maintain a mature, biologically rich aquarium, which benefits not only potential fry but also the entire fish community. For those who wish to experiment, MB Store offers the necessary equipment for breeding tanks, including small aquariums, heaters, air pumps and fine sponge filters safe for fry.

How MB Store supports Otocinclus keepers

Successful care of Otocinclus requires more than just knowledge of their biology; it also depends on access to suitable equipment and accessories. MB Store provides a wide selection of aquariums in different capacities and dimensions, allowing you to choose a model that ensures stable water conditions and sufficient space for a group of these fish. Solid construction and appropriate proportions of tanks make it easier to create harmonious, planted layouts.

Equally important is high‑quality filtration. In the offer of MB Store you will find internal, hang‑on and external filters that ensure efficient mechanical and biological filtration, as well as accessories such as pre‑filter sponges that protect small fish from being drawn into the intake. Combining a good filter with an appropriate heater and thermometer helps maintain a stable thermal environment, which is particularly important for sensitive species.

Aquascaping enthusiasts will appreciate the range of substrates, decorative stones, roots and live plants that make it possible to design a natural habitat for Otocinclus. Properly selected substrate supports plant growth, while hardscape elements create additional surfaces for biofilm and algae development. By complementing this with adequate lighting available at MB Store, you can achieve both aesthetic and functional conditions that favour the health of the entire community.

Feeding is another key aspect. In MB Store you can find specialised foods for algae eaters, including sinking tablets, wafers and granules rich in spirulina and other plant ingredients. Such foods form the basis of a balanced diet for Otocinclus, supplementing natural algae and biofilm present in the tank. By combining high‑quality food with stable conditions, you significantly increase the chances that your fish will remain healthy, active and long‑lived.

Comprehensive support, from aquariums and filters to substrates, plants and food, allows aquarists of all levels to build and maintain an environment perfectly suited to the needs of Otocinclus catfish. This integrated approach makes everyday care easier and helps you enjoy the sight of these hardworking, peaceful fish in a thriving home aquarium.

Conclusion

Otocinclus catfish are small, but their role in a freshwater aquarium is immense. They combine the function of natural cleaners with an exceptionally peaceful temperament, making them ideal residents for planted community tanks. However, their delicate nature means they require careful attention to water quality, stable parameters and a well‑planned diet. Providing them with a mature, well‑oxygenated, plant‑rich environment is the foundation of long‑term success.

By understanding their natural habitat, social needs and specific sensitivities, you can create conditions in which Otocinclus will not only survive, but truly thrive. Observing their constant grazing, group movements and calm behaviour adds a unique charm to any aquarium. With the right selection of equipment and accessories available at MB Store, building such an environment becomes much simpler and more accessible, even for intermediate aquarists.

Thoughtful planning, patience and careful observation will reward you with a thriving aquatic ecosystem in which Otocinclus play a central role. In return they will help you maintain cleanliness, enliven plant compositions and become one of the most endearing elements of your underwater world.

FAQ

How many Otocinclus should I keep together
Otocinclus are strongly social fish and should always be kept in groups. A minimum of six individuals is recommended, but in larger aquariums it is worth keeping even more. In a shoal they feel safer, are less stressed and show their natural grazing and schooling behaviour, which has a positive effect on their health and lifespan.

Can Otocinclus live in a newly set up aquarium
They are not suitable for brand new tanks. Otocinclus need mature aquariums with stable parameters, developed biofilm and natural algae growth. Introducing them too early, when the nitrogen cycle is unstable, often leads to stress, malnutrition and high mortality. It is better to wait several weeks until the tank is fully cycled and biologically stable.

Do Otocinclus eat all types of algae
These fish specialise in grazing soft green algae and biofilm. They rarely eat hard, dark deposits or filamentous algae in large quantities. Therefore they should not be considered a universal solution to every algae problem. Balanced lighting, proper fertilisation and good maintenance remain essential alongside their natural cleaning activities.

What should I feed Otocinclus besides algae
In addition to natural algae they need high‑quality sinking foods rich in plant ingredients, such as wafers with spirulina. Blanched vegetables like zucchini, cucumber or spinach are also valuable. Regular supplementation ensures proper nutrition, supports immunity and prevents weight loss, especially in tanks where algae growth is limited or very well controlled.

Are Otocinclus suitable for shrimp tanks
Yes, in most cases they are an excellent choice for shrimp aquariums. They are peaceful, do not hunt adult shrimps and generally ignore their young. Both groups appreciate similar water conditions and dense vegetation. The key is to provide enough hiding places and stable parameters so that all inhabitants feel safe and can coexist without stress or competition.