Complete Guide to Otocinclus Catfish Care, Diet, and Breeding

Otocinclus on a tank

As a seasoned fishkeeper with over five years of experience, I’ve had the pleasure of diving into the world of aquatic companions and exploring their unique needs and behaviors. One species that has consistently captured the hearts of fellow fishkeepers is the Otocinclus catfish. These diminutive yet charismatic creatures bring a special charm to any aquarium, and today I’m thrilled to share my firsthand insights on their care, diet, breeding, and more.

Introduction: The Otocinclus Catfish

Otocinclus catfish, often affectionately called “otos” or “dwarf suckers,” is a favorite among fish enthusiasts for various reasons. Their charming appearance, peaceful demeanor, and algae-eating habits make them a valuable addition to any community tank. These small catfish originate from South America and have earned their place as efficient tank cleaners and delightful companions.

Types and Characteristics

Within the Otocinclus genus, you’ll find several species, each with its own unique features. There are about 20 species of otocinclus catfish in the Loricariidae family, with common species in the aquarium hobby including O. vittatus (common otocinclus), O. macrospilus (dwarf otocinclus), and O. cocama (zebra oto).

Otocinclus affinis is the most prevalent variety, distinguishable by its slender body, subtle patterns, and distinctive sucker-like mouth. Otocinclus cocama boasts striking stripes, while Otocinclus macrospilus showcases elegant spots. Each type brings a touch of individuality to your tank.

Otocinclus affinis

Otocinclus catfish typically have a black horizontal line, a dark grayish-brown back, and a white belly. They have slightly flattened heads with eyes on either side, which gives them lateral vision. One of their most unique morphological characteristics is the presence of a suction cup in their mouth. This serves them both to feed and to fixate on rocks or plants. This feature is particularly useful in their natural habitat of rivers with currents.

They are small fish that range from 1.5–2 inches (4–5 cm) in length. Unlike many other species of catfish, Otocinclus is diurnal and active during the day. While they sometimes swim in groups, they mostly mind their own business and can be found grazing or resting on the plants and flat surfaces of the tank.

tank size and tank parameters

Providing an optimal environment is crucial for the well-being of your Otocinclus catfish. These social creatures thrive in groups, so a tank size of at least 20 gallons is recommended to accommodate their school. They prefer soft, slightly acidic water with a pH range of 6.0–7.5, a temperature range of 72-82°F (22-28°C), a water hardness of 4°–12° dH, and 3°–10° kH.

A good filtration system with a GPH rating of four times the volume of your aquarium is essential to maintaining water quality and keeping the tank clean. Make sure the filtration system is mature enough to keep the water parameters in check. To maintain a healthy environment for Otocinclus catfish, keep nitrate levels between 0-20 ppm (parts per million) and ensure that there are no measurable levels of ammonia or nitrite.

Otocinclus DIET: What to feed them

Otocinclus catfish are herbivores that feed on algae and slime (biofilm) that build up on plants, rocks, hardscapes, and tank walls. However, since aquascapers do not appreciate algae growth in their tanks and take measures to prevent it, supplementing the Otocinclus diet is essential. Complementing their diet with other foods such as algae wafers, blanched zucchini, cucumbers, carrots, or even blanched or dried mulberry leaves, is recommended.

To prepare mulberry leaves, you can either freeze them to dry or blanch them with hot water. Once they are dried or blanched, put them in the tank and wait for them to sink. You can also weigh them down if needed. For blanched zucchini, cut it crosswise and boil or blanch it for a few minutes until soft. Cool it before putting it into the tank. You can weigh it down with a fork or a wooden stick.

You can feed your otocinclus twice or three times a week, depending on the level of algae and biofilm growth and the number of otos in your tank. Observe your otos to see if they have pearl-shaped bellies. If they are always lean, you can feed them every other day. Do not let them starve for too long because they have bacteria in their gut that help digest their food. Without a stable food supply, the bacteria start to die, and the Otos are unable to process their food.

It is also important to keep live plants and driftwood in the aquarium to encourage biofilm growth. This will provide Otocinclus with a natural source of food and help maintain their health.


The otocinclus lifespan is typically around three to five (3-5) years when kept in captivity. However, receiving poor care and living in a stressful environment can have a significant impact on their life expectancy. To ensure that your otocinclus catfish live a long and healthy life, provide them with a well-maintained aquarium that meets their basic needs. This includes keeping the water clean and maintaining good water quality, providing them with a balanced diet that includes algae and other supplements, and ensuring that they have plenty of hiding places and room to swim. By following these guidelines, you can help your otocinclus catfish live a long and happy life in your aquarium.

Best Tank mates for Otocinclus

Otocinclus catfish are peaceful and shy fish that are easy to care for and fun to watch. They are known for being good community tank fish, but they’re not compatible with every type of fish out there. You need to choose tank mates carefully to ensure the safety of the otos. Here are some suitable tank mates for Otocinclus catfish:

  1. Small Tetras: Many small tetra species, such as Neon Tetras, Ember Tetras, and Glowlight Tetras, can coexist peacefully with otos. They occupy different niches within the tank and generally have a calm temperament.
  2. Corydoras Catfish: Corydoras catfish share similar requirements with otos, preferring soft, well-oxygenated water. They are bottom-dwellers and won’t compete for food, making them excellent companions.
  3. Rasboras: Peaceful rasboras like Harlequin Rasboras and Chili Rasboras are a good fit. They inhabit the upper to middle levels of the tank, so they won’t interfere with the otos’ activities.
  4. Small Gouramis: Dwarf Gouramis, like the Honey Gourami or Sparkling Gourami, can work well as long as the tank is large enough to provide space for both species. Gouramis are generally calm and won’t bother otos.
  5. Small Shrimp: Certain species of dwarf shrimp, like Cherry Shrimp or Amano Shrimp, can be suitable tank mates. However, ensure that the shrimp population doesn’t grow excessively, as larger shrimp numbers might compete for food resources.
  6. Livebearers: Peaceful livebearers like Endler’s Livebearers or Guppies can be compatible, as they inhabit different tank areas and have minimal aggressive tendencies.
  7. Snails: Adding a few species of peaceful snails, such as Nerite Snails or Malaysian Trumpet Snails, can contribute to the cleanup crew without bothering otos.

Remember that tank size, water parameters, and compatibility with the specific otos’ needs should always be considered when choosing tank mates. Introducing any new fish to an established tank should be done gradually to minimize stress and potential conflicts. Monitoring the behavior of all tank inhabitants is essential to ensuring a harmonious and thriving aquatic environment.

Otocinclus Breeding

Otocinclus catfish typically reach sexual maturity between six and nine months of age. Breeding them in captivity requires meticulous attention to their environment and care routines, and is usually recommended for advanced breeders.

To stimulate breeding, several conditions need to be met. The tank water must be kept impeccably clean, and the fish should receive a protein-rich, nutritious diet. Raising the water temperature to around 79°F (26°C) can also encourage mating behavior, mimicking their natural habitat.

When the fish are ready to breed, male Otos will actively chase the females around the tank before fertilizing the eggs. The females lay their eggs on surfaces like plants and bogwood, and these eggs will hatch after several days. The fry, upon hatching, feed on bacteria and algae present in the tank.

Tips for Buying Otocinclus

Novice aquarists often face frustration with the significant mortality rate of Otocinclus catfish shortly after purchase. These delicate fish, primarily sourced from the wild, endure harsh shipping conditions, including fasting for up to 48 hours to minimize waste during transport. Arriving at fish stores, they’re further stressed due to overcrowded tanks and insufficient algae, their primary food source. Starvation and stress are the primary culprits behind their high mortality rates.

Here are some tips when buying Otocinclus from the fish store to greatly increase their survivability:

  • Choose fatter fish and avoid skinny-looking ones.
  • Look for healthy fish that have bright eyes and a bigger body size.
  • Avoid fish seen struggling to swim or breathe.
Choose the one with round, pearl-like bellies. Photo: オトシンクルス

To prevent Otocinclus from dying in the first few hours, acclimate them slowly to the new environment. When introducing dwarf suckers to my tanks, I use the drip method to prepare them for their new home. This will prevent temperature and pH shocks that will stress them. Make sure to put them in a mature tank where the water parameters are already stable because fluctuating water parameters will stress and eventually kill the fish.

Frequently Asked Questions (FAQs)

Here are some frequently asked questions about Otocinclus catfish:

Will Otocinclus eat my plants?

Otocinclus are herbivores but they do not eat live plants. However, live plants are necessary to encourage biofilm and algae growth for the otocinclus to graze on.

What fish eats Otocinclus catfish?

Otocinclus catfish are generally peaceful and do not have many natural predators. However, larger fish such as cichlids, angelfish, and goldfish may eat them if they are small enough to fit in their mouths. It’s important to keep Otocinclus catfish with compatible tank mates that won’t harm them.

Does Otocinclus eat black beard algae (BBA)?

No, otocinclus does not eat black beard algae (BBA). They are herbivores, but BBA is too tough for them to eat. They prefer to eat soft, green algae and diatoms.  However, they may nibble on black beard algae if it is the only food available, but they will not be able to control its growth.

Do Otocinclus catfish jump out of the tank?

Otocinclus catfish are not known to jump out of tanks as often as other fish species. However, it is still possible for them to do so, especially if they are stressed or unhappy.

How many otocinclus can I keep in a 10-gallon tank?

The general rule of thumb for stocking a fish tank is one inch of fish per gallon of water. However, otocinclus are small fish that only grow to about 2 inches long, so you could technically keep up to 10 otocinclus in a 10-gallon tank. If you are considering keeping otocinclus in a 10-gallon tank, I recommend starting with a group of 6. This will give the fish enough space to swim around and socialize, and it will also help to reduce stress. You can always add more otocinclus later if you have the space.

Does otocinclus eat hair algae?

No, otocinclus does not eat hair algae. They prefer to eat softer algae such as green dust algae, diatoms, and brown algae. They may also eat some plant matter, but they are not effective at controlling hair algae.

Does otocinclus eat green spot algae?

Otocinclus catfish are not known to eat green spot algae. Green spot algae is a type of cyanobacteria that is difficult to remove and can be harmful to fish. Otocinclus catfish prefer to eat softer algae, such as brown diatoms and soft green algae.

Why You Should Add Otocinclus to Your Tank

Otocinclus catfish are small, peaceful, and algae-eating fish that make great additions to freshwater tanks. They are not demanding and can be kept in a variety of tank conditions. However, they do best in groups of at least six and should not be kept with aggressive or large fish. If you are looking for a low-maintenance fish that will help keep your tank clean, otocinclus is a great option.

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