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Otocinclus Catfish: Complete Care Guide (Diet, Tank & More)

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Smaller species of catfish are a great addition to any freshwater aquarium. They are docile in nature and will assist in cleaning the tank. 

The following guide will give you all of the information you need to know to make sure your otocinclus catfish will thrive in their new environment. 

Otocinclus Care Guide

Common Names:Otocinclus, otocinclus catfish, dwarf sucker, dwarf armored catfish, oto, oto cat
Scientific Name:Otocinclus sp.
Adult Size:1-2 inches
Minimum Tank Size:10 Gallons
Otocinclus Aquarium Fish Close Up on Cucumber

Otocinclus catfish are popular amongst freshwater hobbyists. They do best in groups of 6 as they are pleasant little fish and also social. They are easy to care for if the correct parameters are met. They are algae eaters and help keep your freshwater aquarium clean.

Otocinclus Appearance & Temperament


Otocinclus catfish are peaceful fish that are bottom-feeders. They are great additions to planted aquariums so long as they are cared for.  Ottos are algae eaters and will keep the algae at bay in your tank. 

With an oto, you can add multiple to your tank without putting any danger on your other fish. They are nocturnal fish that spend most of their time latched onto different surfaces, eating algae. 


Smaller than most freshwater fish, otos only grow up to 1-2 inches. The female otto is bigger and broader than male otos. The Giant Otocinclus is considered extra large for the species as it can grow up to 4 inches in length. This is still on the small side for freshwater fish.

Colors and Markings

Otocinclus have a narrow cylinder-shaped body with short fins, they have strong mouths for latching to different surfaces to feed.

Between their esophagus and stomach, is a hollow space that gives them the ability to breathe limited air in the water. This allows them to go to the surface for air if the water is not oxygenated enough.

Rows of armor plating along their body set them apart from other species of catfish. Different colors and patterns are dependent on the type of otocinclus catfish.

The common otocinclus have a white lower body plight from speckled brown upper bodies by a brown stripe. Their fins are almost transparent.

 Examples of Other Popular Otos Include

  • Zebra Otocinclus: These otos have vertical black and white stripes all over their body, just like a zebra. The zebra oto comes in different color variations such as orange zebra.
  • Giant otocinclus: These extra large ottos have a mottled gray or brown coloring.
  • Silver Otocinclus: Similar to the common otto, they have the same stripe down the body except for silver. 

However, otos, no matter the kind, will be dull in color when stressed or are living in poor water conditions. When breeding the color of the otto will become brighter and bolder which typically attracts mates.

Gender Differences

Female and male ottos have very similar colors and patterns. When they are young it can be hard to determine the difference.

As they mature, however, the females will become slightly larger and wider, even more so when full of eggs. While the males are smaller and thinner than the females. 


With proper care, healthy ottos can live in captivity for an average of 3-7 years. However, in the wild, they typically only live up to 2-3 years.

What to Feed Otocinclus Catfish

Otocinclus are bottom feeders which means their diet consists mostly of algae, plant matter, and bacteria. Ensuring there are plenty of sources of algae inside your tank is the best way to copy their diet in the wild. 

If you have a larger group of the otocinclus, then you may notice that they are eating the algae faster than it is growing. If this is the case, adding more plants in the tank for a larger number of ottos would be ideal.

However, there are ways to supplement natural algae in case of a shortage in your tank. There are commercial algae wafers that you can have on hand if needed.

Also feeding blanched vegetables such as spinach, lettuce, or zucchini, can be a supplement for natural algae.

With the algae wafers or blanched food, you will want to make sure they are in small pieces so they are easy to swallow.

Place the small food pieces in the tank and after about 24 hours remove any remaining food.

This species of fish has 24 hours to eat their food. This is because otocinclus catfish are grazers, which also means the chances of overfeeding them are lower. 

Tank Mates for the Otocinclus

Since the Otocinclus catfish are such small and peaceful fish, they are essentially easy prey for bigger fish. Ideal tank mates are going to be peaceful and be similar to their small size.

Some great options in tank mate for the otocinclus catfish are:

  • Other Oto Catfish (Keep in mind they do need to be in groups of at least six of their kind)
  • Tetras
  • Mollies
  • Guppies
  • Harlequin Rasboras

This is only a few examples of tank mates that are suitable to the oto catfish, other non-fish additions to their tanks can be shrimps and freshwater snails.

As mentioned above, their size and temperament make them easy targets for larger fish. You will want to avoid predatory fish such as Oscars or cichlids.

Housing Otocinclus: Tank Setup

When setting up a tank it is always important to replicate the species’ natural habitat to have healthy fish that will thrive.

You can easily replicate their natural environment by adding in the right substrates, vegetation, and decor.

However, keep in mind that the minimum tank size you can have for the Otocinclus catfish is 10 gallons. For larger groups greater than 10 fish, opt for a 20-gallon tank instead. 

Otto catfish are bottom dwellers and they are also known for digging in the substrate. Because of this, you want to avoid sharp or coarse substrates that can cause injury to them.

Instead, opt for a fine-grain sand substrate, this is not only safer but is most like their natural environment as well. 

Because their natural habitat has moderate vegetation, standard aquarium lighting is perfectly suitable for the Otocinclus catfish.

Decorations are great for creating shelter and hiding spots. Some decorations such as live plants, like the Staurogyne repens,  can be used to promote algae growth in the tank which is perfect for the otocinclus catfish. Other decorations such as caves, driftwood, and rocks are also ideal additions to your tank.

You will want to make sure you have a good filter that is suitable for the Otocinclus catfish. Even though these are hardy fish they are sensitive to poor water.

A good filter minimizes ammonia and nitrite levels in the water. Also, make sure the filter current is not too strong as they are used to slow-flowing waters.

Ideal Water Conditions & Water Quality

As mentioned previously the otocinclus catfish come from the warm soft waters found in South America. Even though ottos are hardier fish they need to have stable water parameters. 

They can not handle parameters that are fluctuating. Keeping a clean tank with steady parameters is very important. Follow the right parameters below and these catfish will be thriving!

  • Water Temperature: You will want to keep your water temperature on the warmer side of around 72–79°F.
  • pH Levels: Otocinclus are used to slightly more acidic waters at about 6.8–7.5 pH, which may not be suitable for other species.
  • Water Hardness: Oto catfish are used to very soft waters in South America, the water hardness of 7.0–15.0 dGH is ideal. 

Breeding Otocinclus Catfish

Breeding otocinclus catfish can be very difficult and because of this, some will recommend that only professional breeders take on the challenge. There is not a lot of information right now on breeding otocinclus catfish due to a lack of research capabilities. 

There are, however, things that you can do in order to encourage your ottos to mate. This includes ensuring that the water is pristine in the tank, as well as water temperatures above 79°F.  You should also feed the otos a protein-rich diet.

They are egg-laying fish, and they can lay up to 50 eggs. They lay in batches of about 3-6 eggs. The eggs are also sticky and will stick to plants and bogwood.  

If you happen to witness when otocinclus catfish start to mate, you will see that the male actually chases the female around prior to fertilization. Once the male catches the female they will go into a “T “ position, which at this time the female will release the eggs from her body, then hold them with her fins. 

The female will then stick her eggs to a suitable surface and the male will fertilize the eggs. This process will keep repeating until the female is done laying eggs. After several days the eggs will hatch and you will have the difficult task of raising the fry.

Buying Otocinclus: Detailed Guide

Buying otocinclus catfish can be quite tricky. It is a very common issue amongst tank owners to have a large number of losses of new otos within the first few weeks despite ideal water conditions. There are a few things that could be the cause of this problem. 

Some theories include: 

  • Chemical Poisoning: Some believe that this issue is caused during capture. A chemical, such as cyanide, is used to capture fish in the wild. This chemical slows down the fish and can even temporarily paralyze them, making it easier to catch large numbers of fish. 
  • Shipment: After the fish are caught they are shipped to whichever destination they are going. This is very stressful on not only the oto but any species of fish. It is so stressful that only very healthy and hardy fish can handle it. 

Issues during shipment include oxygen level changes, temperature changes, irregular lights, dramatic movements, and even vibrations that can cause a variety of diseases in the fish.

Another issue during shipment is that it is typically common for the fish to be starved 24-48 hours before final bagging at shipment, leaving the fish to starve to death in transport. This leaves a lot of fish dead on arrival.

With this information in mind, you will want the healthiest ones you can find to avoid dramatic losses within the first few weeks or months.

That being said, tank-bred otos are the better option. So, how can you tell if they are healthy?

  • Ask Questions: If you are buying them from a fish store, ask how long they have had them. This is because it is common for them to die shortly after arriving at fish stores. The longer they have been there the better!

Also, ask about what they are being fed, if they aren’t being fed the proper diet, only flake food for example, do not buy them- they are likely to live a short life. 

  • Check Their Appearance: Check if they have plump bellies. This does not mean they are healthier. Rather, if they appear bloated they may have an infection. 

Take note of their colors, are they what they should be? Avoid them if they have white or bloody marks, this could be injury or disease. It is good to also check their fins.

They can sometimes appear rounded from damage or stress. Although if it appears to be minor damage, don’t stress too much as this could be a minor injury that may have occurred before captivity. 

Once you have found decent otocinclus catfish to buy and bring home, ensure the tank has been cycled and fits their specific tank requirements. 

It is also recommended to quarantine them by themselves for a few weeks. This ensures that they are healthy, and you do not run the risk of having your other fish catch a disease. 

Wild Otocinclus: From Origin to Aquarium

The Otocinclus is typically found in the shallow slow flowing streams and rivers in South America. These South American waters are moderately vegetated and have plenty of sunlight. 

The rivers and streams are soft waters and have a sandy riverbed. Here is where you will find the Otocinclus! They are typically attached to driftwood, rocks, and other surfaces feeding on the algae.

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