Otocinclus – Dwarf Sucker

A catfish devoted to eating algae, and sometimes referred to as dwarf suckers or otos, Otocinclus are the shy, peaceful catfish who happen to have a penchant for feasting on algae.


The Otocinclus, the wonderful algae eater
  • Experience Level: Beginner
  • Hardiness: Moderately Hardy
  • Minimum Tank Size: 10 gal (40 L)
  • Maximum Size: 1.5 inches (4 cm)
  • Temperament: Peaceful
  • Temperature: 72 – 82° F (22 – 28° C)
  • pH Range: 5.5 -7.5
  • Water Hardness: 7 – 15 dGH
  • Diet: Herbivores

Table of Contents




Size and Appearance


Care Guide


Tank Mates


Diet and Feeding



The addition of these black striped fish to a communal aquarium is a low-effort way to keep your tank tidy, although their inclined nature towards producing a lot of waste does lead to a rise in nitrate levels.

Traverse through regions in South America, like Venezuela and Argentina, and you’ll discover the natural habitats of these catfish, also nicknamed Otos or Dwarf suckers.

Size and Appearance

Resembling common otos species, these dwarf suckers are undersized catfish, rarely exceeding their two-inch size during growth, with some adults only reaching about an inch. Their overall shape – a narrow cylinder – tapers around their head and tail. The females exhibit higher bulk and size than their male counterparts.

Otocinclus uses their large mouths as the perfect tool to clean the algae covering the aquarium walls. Their body is adorned with brown stripes which subsequently fade on their fins. Additionally, a dark spot stands out on its tail, and their body is enveloped in an armor-like protective shell, safeguarding them from the attacks of aggressive aquarium companions or the rough edges of certain aquarium substrate surfaces.

Eyes on their slightly bent, elongated body might seem to be on the sides, but you would be able to spot them from underneath. The mouth is downward-facing, and they have see-through fins; however, they lack both adipose and barbels fins.

The body of an otos boasts a distinguishing greyish-green color, a dark back, a white belly tinged with yellow. Their breathing system is unique – instead of using gills as most fish do, they have a hole connecting their esophagus and stomach, limiting air intake.

Being algae eaters, dwarf suckers considerably reduce the effort of hobbyists in maintaining aquarium water. Unlike other catfish species, otos are comfortable in smaller areas of water, such as tiny rivers. Their maintenance is low-key, making them a particularly beginner-friendly choice.

Reliably eliminating algae, these docile fish are resilient and can exist within a broad spectrum of water conditions. Preferring to lay low in the bottom strata, they purposely avoid coming in the way of other species.

Despite their tiny size, they get startled easily and are often the target of larger fish. In trying to escape danger, they love to join a school, whether in their natural habitat or an aquarium. Though otos prefer mingling in much larger groups than smaller ones, they remain active even when by themselves in the water.

Sometimes, to guard themselves, the otos mimic the corydoras, whose spikes contain venom. Usually more active during the day than at night, they may become nocturnal in a communal tank housed with larger aggressive fish. Even though they’re timid, they’re swift swimmers.

If adequately taken care of and fed under suitable water conditions, an oto raised in an aquarium can live up to five years.

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Care Guide

  • Minimum Tank Size: 10 gal (40 L)
  • pH Range: 5.5 – 7.5
  • Water Hardness: 7 – 15 dGH
  • Temperature: 72 – 82° F (22 – 28° C)
  • Lighting: Moderate, diffused lighting
  • Substrate: Fine sand/gravel
  • Brackish: No
  • Water Flow: Weak/Low
  • Tank Region: Mainly Bottom

Otocinclus have minimal care requirements; instead, they offer more assistance. This makes them a highly desirable inclusion for hobbyists who crave healthy fish but with little to no fuss. They present more advantages as compared to other types of freshwater fish.

Although they’re adaptably swift compared to other small fish species with specified needs, it’s essential to keep an eye on otos. In the wild, these fish are often observed by passionate aquarists as they latch onto algae-laden rocks and surfaces. As such, your aquarium would need to replicate this by having plenty of surfaces like rocks, wood, and others.

Triggering algae growth may become necessary if it doesn’t occur naturally, as otos catfish enjoy it greatly. A grainy or sandy substrate becomes a better option when compared to a gravel substrate. This prevents any injuries from occurring as they dwell at the tank bottom.

Despite their protective body covering, remember that a severe scratch may eventually cause more pressing issues like infections. Try to include items that the otos can use for refuge when either stressed from pursuing larger tank mates or when weary.

Otos naturally shyer by nature, hence require plants for protection from their surroundings. They also require the right amount of light. While they can thrive with natural light, you can also consider using LED and placing plants strategically to create shade.

Otos are sensitive to nitrates, so if you detect it during a water test, perform an immediate water change. Moreover, you can also use nitrate pads to regulate nitrate levels effectively. If high nitrate levels are detected, it would be best to remove some fish from the communal tank.

Otos are freshwater catfish who hail from slow-moving small water bodies. Weekly water changes are necessary to maintain water quality. They flourish best within a water temperature range of 72 to 82°F, and a pH level that falls within 5.5 to 7.5.

Undergoing regular water changes will help get rid of ammonia and nitrates. Your Otocinclus pet fish will flourish in oxygen-enriched water. Nevertheless, you can also utilize a regular tank pump and nitrate filtration system.

For an Otocinclus, the aquarium should have a minimum size of 10 gallons. This would provide ample space for a group of six same-species Otocinclus fish. Large aquariums can disconcert otos as they prefer to easily spot members of their group, or else they become frightened. Smaller tanks, on the other hand, are unable to produce the right amount of algae that the otos require as nourishment.

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The helpful Otocinclus

The Otocinclus – A welcome addition to any cleanup crew

Tank Mates

Three significant ways can be followed to choose an Otocinclus tank mate; known to be shy and jittery but sociable, Otocinclus are a peaceful breed. Hence, they should be paired with a fish that portrays a temperament similar to theirs. For instance, a hostile tank mate will constantly pester and intimidate the otos. Some fish are given to sheer hostility about their mate or protecting their young, while others can be temperamental about food and territory. Identifying the root of the troubling behavior and striking a balance makes it easier to select a suitable tank mate. For example, if the tank mate is aggressive about their young, moving them to a breeding tank will resolve the problem.

  • Recommended otos tank mates:
    Same-species companions: otos engender similar social conduct. They function better in larger groups but can co-exist in smaller communities.
  • The corydoras: these catfish make perfect tank pairs for Otocinclus due to their similar behavior. They are as shy as otos yet sociable in the company of properly sized fish. They’re also dynamic and belong to bottom strata breeds.
  • Invertebrates, such as shrimps and snails: bamboo shrimps are a wise choice because they are harmless. They don’t have any sharp body parts to defend themselves and also, they are neither hostile like otos.

Other great tank mates include:

  • Mollies
  • Cherry barbs
  • Harlequin Rasbora
  • Tetras
  • Guppies
  • Dwarf Gourami
  • Angelfish
  • Danios
  • Zebra Loaches

Rabbit snails, Malaysian trumpet snails, gold Inca snails, ivory snails, Japanese trapdoor snails, Ramshorn snails, and mystery snails all are so well-suited tank mates for the Otocinclus. Other shrimp species include red cherry shrimp, Amano shrimp, vampire shrimp, and ghost shrimp. However, don’t forget to ensure the algae in the tank is enough for all tank mates.

Otocinclus cannot share a tank with the cichlids, goldfish, Jack Dempsey striped convict, Oscars, and Texas Cichlids.

Crabs will also attempt to capture and eat the Otocinclus. Additionally, crayfish are not suitable tank mates. Always consider the behavioral traits of potential tank mates and their compatibility with the Otocinclus catfish.

Feeding Guide

  • Diet: Herbavore
  • Frequency: Several small feedings per day
  • Pellet Foods: Yes
  • Flake Foods: Yes
  • Live Foods: No
  • Meat Foods: No
  • Vegetable Foods: Yes

For Otocinclus, the diet mainly comprises vegetarian meals, like algae, which is mostly eaten in their tanks. But in smaller groups, they become more wary of danger and spend more time hiding and escaping than eating properly. Nevertheless, your pet fish still need to be fed other nutritious foods.

They also feed on aquarium plants and organic-free veggies like cucumber, lettuce, unsalted peas, zucchini, and spinach. Vegetables are good substitutes for meals but algae are more nutritious. Algae wafers are another alternative for fresh tank algae, especially when the growth rate is slower than their grazing habits. Otos also consume biofilm from tank surfaces and catfish pellets.

The leaves on plants like cryptocorynes, Anubias, and java Ferns encourage the growth of biofilm. These are therefore suitable plants to have in your Otocinclus tank. Chop up their food, cook them for a few seconds, and immerse in cold water. After that, you can drop it into your pet’s aquarium, ensuring that it drops to the tank’s bottom.

If they leave any unattended food, execute a water change or remove it before decay sets in. Feeding Otocinclus too much food is both unhealthy and wasteful, so it’s preferable to give them balanced, regular meals.

Sometimes, Otocinclus can develop a stubborn preference for eating only algae and decline to eat any variants. While this isn’t done out of stubbornness or hardiness, it’s more of an inherent behavior as they might not recognize that other types of food are safe to ingest apart from algae. As such, they won’t consume your vegetable or wafer substitutes, choosing rather to starve.

The preferred types of algae for Otocinclus include green dust algae, diatoms/brown algae, and green algae. However, they won’t feed on staghorn algae, black beard algae, or hair algae.

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The breeding process is what makes Otocinclus a hardy fish. For a catfish raised in a tank, the exacting method is tough. They are unusually finicky about their needs during breeding, expecting the simulated environment to be almost the same as their natural habitat. Hence, if you’re thinking of breeding your otos, perform a water change and clean the tank. It’s also wise to put a group of the same-species catfish in the tank so that they can find a mate organically.

Differentiating the male and female Otocinclus catfish becomes crucial because if only males are added, breeding would never occur, as otos display sexual dimorphism. The males are not as bulky and large as the ready-to-mate females. Males also have a genital papilla, which appears as a growth that looks like a nipple at the tail’s lower area.

Feed the otos catfish with healthy and nutritious meals regularly as they prepare for breeding. Increasing the water temperature up to a maximum of 79°F will stimulate spawning since mating drains both the male and the female otos, and the pursuit could go on for hours.

When the freshwater nano fish are prepared, the male otos initiate mating by chasing the female around. He then attempts to form a “T” posture with her, indicating his desire to connect. The oviparous female will then release her eggs onto various flat surfaces in the tank, and the male will fertilize them. The good eggs appear clear with a cloudy inside, while the bad ones are solid white.

It’s essential to separate them as the spoiled eggs carry infection and won’t hatch. The process will continue in patches until the female has released all her eggs. In otos, breeding varies from other fish species as the male doesn’t become aggressive in guarding the eggs. Instead, he considers his job done post fertilization.

The use of a separate breeding tank is recommended to ensure that the other fish don’t consume the eggs or fry. After a few days, the eggs will hatch and the fry will begin swimming in the tank. Initially, otos young feed on algae and bacteria, and later transition to adult meals.

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