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Otocinclus Catfish Care Guide & Species Profile

The Otocinclus fish can be a perfect addition to an aquarium. Caring for the fish is not that difficult. But you need to ensure that the tank conditions are right.

Otherwise, the freshwater fish can die as it is delicate and can’t survive extreme water parameters.

With proper Otocinclus catfish care and feeding, the fish can last for some years. Here, we look at the habitat, feeding habits, behavior, breeding, and other essential information for freshwater aquariums.

Species Overview

Level of CareEasy
AppearanceMost have brown stripes
Life Expectancy3-5 years
Size1 – 2 inches
Tank Size10 Gallons
Water Conditions720F to 790F (220C to 260C); pH 6.8-7.5; Soft water < 15 dH
Tank EnvironmentSandy substrate with cave
Tank MatesNonviolent fish

Otocinclus catfish is a freshwater fish that belongs to the Loricariidae family. The fish is a genus of catfish with over 19 species. It is found in different patterns, colors, and sizes in South America in the waters east of the Andes from Venezuela to Argentina.

Most of them are caught in the wild and bought in large numbers by wholesalers. They are popular among aquarists since they are algae-eaters and help keep the tank clean. Many also add fish to their aquarium due to its unique appearance.

They are found mostly in shallow rivers and streams. The waters where the Otocinclus thrive receive plenty of light that penetrates the shallow waters.

The fish thrives in warm and slow-moving but well-oxygenated water. The surface of the water is covered with a sandy substrate, rocks, and wood. The fish attaches itself to the rocks and substrate in search of algae.



The Otocinclus has a tan body with black peppered marks. The fish has a cylindrical body shape that becomes narrow towards the caudal fin and head. There is a mouth on the fish’s head with which it latches onto the surface of the aquarium to feed on algae.

A unique aspect of these species that distinguishes other catfish is the rows of armor plating on its body. The plating protects the fish from coarse substrates and aggressive fish. A duct between the stomach and the esophagus forms a hallow area that allows the fish to breathe.


The colors and patterns of different species of fish are different. Zebra Otocinclus (Otocinclus Cocama) has black and white stripes along its body.

The stripes are located behind the caudal fin and the head. The stripes of some fish aren’t straight, due to which they are called Tiger Otos.

Golden Oto (Otocinclus Affinis) is named after its distinctive brown color that appears to be close to gold. Silver Oto (Otocinclus Vestitus) has lateral stripes similar to other Oto species. But its color is closer to silver.

Dwarf Oto (Otocinclus Macrospilus) has a dark stripe across its body. The fish has a different caudal fin design as compared to other species. There is a large blotch on the tail, and the lateral stripe of the fish becomes pale before the caudal fin.

Otto Vittatus is the most common species of the Otocinclus fish. The upper part of the fish is speckled brown, while the lower part is white. A brown stripe runs along the side of the head while the fins are transparent in color.


These are small fish that rarely grow to more than 2 inches. Some species, such as the Otocinclus Tapirape, are only an inch long. Otocinclus Flexilis is the largest species of them that can reach 2.2 inches.

Behavior & Temperament

They nonviolent fish that mostly spends time at the bottom of the tank or on the aquarium wall. They usually eat the algae or like to stick to plants and decorations inside the aquarium.

These occasionally rise to the surface to get some air when the aquarium water lacks oxygen. They absorb oxygen through their gills. When they return to the bottom, they don’t need to pump their gills to get oxygen.

Otocinclus are skittish when around larger fish. They tend to dart around the tank when scared. A group mostly sticks together, grazing the same area inside the aquarium.

They keep themselves busy by spending most of their time sucking on surfaces. They eat algae on plants, aquarium walls, and decorative items.

3 otocinclus sucking the glass

Tank Mates

These are peaceful by nature. It would help if you did not keep the fish with aggressive or larger fish species. Avoid keeping an Oto with Goldfish or Crayfish. Aggressive fish like Jack Dempsey, Oscars, Striped cichlids, and other types can kill or injure the fish. Any aggressive or a large fish with a mouth big enough to eat Oto should not be kept in the same tank.

Fish that are compatible include Corydoras Catfish, Angelfish, Dwarf Gourami, Danios, Harlequin Rasbora, Emerald Dwarf Rasbora, Guppies, Tetras, Mollies, Zebra Loaches, and Mollies. You can also keep the fish with invertebrates. Snails and shrimps are everyday tank mates that are compatible.

Tank Conditions

The water inside the tank should be clean but not too clean. The nitrite and ammonia levels inside the tank should be 0 ppm. Water temperature should be between 72F to 79F (22C to 26C).

Soft water with hardness levels less than 15 is ideal for the fish. It would help if you kept the water pH level close to neutral, between 6.8 and 7.5. A standard air pump is necessary for oxidation inside the water.

You should also invest in sufficient LED lighting inside the aquarium to mimic the natural habitat.

A filter is also essential for the aquarium with Oto fish. You should buy a filter that can cycle the water at a four GPH rating. Test kits to test the water quality level and purchase a CO2 injector to ensure optimum condition for the fish.

Tank Setup

Tank Size

Otos are small in size. So, you don’t need a large tank to keep them. A 10-gallon tank is suitable for keeping 4 to 6 of them in the tank. Each additional fish will require an additional gallon of water.

The ideal tank should have a large surface area at the bottom. It s is because the fish tend to spend most of their time eating algae at the bottom.

Make sure to change half of the water in the tank every week. But avoid a sudden shift in water temperature or other parameters as this can create stress and cause them to die prematurely.

Plants & Décor

The Otocinclus thrives in a tank with a sandy substrate and decorative items, including shells and caves. The tank should have a growth of soft green algae. They feed on algae that grow on hard surfaces inside an aquarium. Make sure the aquarium has some algae.

Select a fine-grained sandy substrate. Avoid coarse substrates as they can scratch their body and injure them.

Consider having plants in the aquarium-like Staurogyne repens, Java moss, Anubias, Cryptocoryne, and Cabomba to promote algae growth. They tend to stick to the plant surface but eat the algae instead of the plant.

Food & Diet

Otocinclus are herbivores and mostly eat algae inside the tank. You can also feed them supplements like algae wafers. Some of these also eat fresh vegetables, such as spinach, lettuce, and zucchini slices.

You should add a few slices inside the tank. If the fish doesn’t seem interested in eating the fish, take out the slices before they decompose and degrade water quality.

Some Oto species also eat other food items, such as bottom feeder pellets and sinking krill pellets. It would help if you experimented around a bit to find out the best food item for your fish. Monitor the algae level inside the tank to determine how much supplementary food to give to the fish.

Breeding Guidelines

Otocinclus fish’s breeding is not easy. There is little distinction between males and females. Fully grown males are slightly smaller and less plump than adult females. But it is not easy to discern the differences between them.

Breeding is by chance, and you will rarely see the mating process. They are picky and do not always mate. You can encourage them to mate by increasing the temperate a bit. Rising temperature in the wild is a natural cue for the fish to mate. But it would help if you kept the temperature below 790F (250C).

Males will chase the females around the tank when they are in the mood to mate. They will get into a T position causing the females to release and hold the eggs using the ventral fins.

Once they have found the right place to place the eggs, the males will fertilize them. The mating process will continue until all the eggs are laid and fertilized. Females can lay up to 50 eggs during a mating session.

To prepare for the breeding, you should feed a diet rich in protein, such as brine shrimp and daphnia. The tank should also contain a sufficient amount of plants that will hold the cluster of eggs released by the females.

Unlike some other fish like the Convict cichlid, Otocinclus don’t display parental instinct. Their eggs will hatch a few days after mating. You will see the fry swimming toward algae and other microbes inside the tank.

Common Diseases

Otocinclus are prone to common diseases that afflict other fish. Some of the diseases that can afflict them include gold dust disease, white spot disease, and cotton mould.

White spot disease affects a lot of fish, including these fish. A visible sign of the disease includes white spots on the gills and bodies of the fish.

These white spots are caused by a protozoan that infects the fish. You can see the affected fish rubbing its body against the surface due to irritation. They may also gasp for breath and become reclusive. Quarantine the affected fish in a separate aquarium and raise the temperature to 86F (30C). Adding aquarium salt is another way to treat the fish afflicted with the disease.

Cotton mould or Saprolegniasis is another common disease that can afflict them. The parasitic disease is caused by a fungus called the Saprolegnia. Infected fish have a cotton-like fluffy growth on the gills, fins, and body.

It can prevent the regulation of water and salts in the fish. The fish moves in an uncoordinated fashion and display respiratory complications.

The mortality rate is high with Saprolegniasis but can be treated. Aquarists have reported success through substances like hydrogen peroxide, malachite green, and formalin.

Gold dust is yet another common parasitic disease among Otos. The parasite attaches to the skin and gills of the victim. The infected fish has a yellow spot over the body. Signs of the disease include rapid breathing, lethargy, labored breathing, and loss of appetite. The disease can be treated using malachite green, methylene blue, acriflavine, and copper sulfate.

Roundworms are also capable of causing different problems. You can see the worm protruding from the bottom of the host. Loss of appetite and lethargy are the two common signs of roundworm infection.

Feeding your fish with feeds soaked in levamisole or thiabendazole can help in treating the condition. You can also treat the illness by mixing parachloro meta xylenol in the aquarium water.

The most common cause of diseases is a dirty tank. You should ensure that the tank is kept clean at all times. Should alsoThe water temperature, pH levels, and nitrate levels. Should also keep it within an acceptable range. Every week you should replace about 25 to 30 percent of water inside the tank.

Dwarf catfish eating cucumber

Where to Buy?

You can get an Otocinclus from most pet stores. But you should pick healthy ottos if you want them to live for two to three years. A lot of times, they are not taken care of well in pet stores. The weak fish die when bought and place in the aquarium.

To ensure that you buy healthy ones, you should ask some questions from the pet store worker. Please find out about what food they feed to the fish. Leave the store immediately if they say that the fish are fed ‘flake food.’ It would help if you also were wary of the store worker being vague about the fish’s diet.

A close inspection of the fish can also reveal whether the fish are healthy or weak. The bellies of the fish should be plump but not bloated. You should also ensure that the fish are of the right color. Avoid buying fish with strange spots. Also, it would help if you inspected the fins to ensure that they are sharp and erect. Rounded fins are often due to stress that contributes to an early death.

How to Introduce Otocinclus Catfish to Your Aquarium?

Otos are sensitive fish that can become easily stressed due to a change. You can use the drip method to acclimate the fish to the new surroundings.

The process involves putting the fish in a clean plastic bucket with a couple of gallons of water. Next, you should put a standard air valve on one end of your aquarium air hose. Open the air valve and fill the air hose with aquarium water.

Now, clip the hose containing aquarium water into a plastic bucket containing the fish. The water will fill the bucket in drips, and it will take about an hour to fill the bucket. After the bucket is full, you should gently dump the fish into your aquarium.

You can also buy a drip acclimation kit from a pet store. The drip kit has a u-shaped tube on the intake side and a plastic valve on the output end.

Using the drip acclimation method will reduce the stress associated with moving fish from one tank to another. It will reduce the risk of death among Otos when they are placed in a new environment.

Wrapping it All Up

Otocinclus Catfish are attractive and functional fish that are great for the aquarium. The fish do a great job of keeping algae in control inside the tank. The fish will turn your algae problem into a delicious meal.

A planted aquarium with caves and rocks is recommended as there will be plenty of hiding places. Make sure that there is high aeration, good water movement, and filtration.

You won’t have to feed anything if the aquarium has high vegetation and algae. It makes them one of the easiest fish to keep in the aquarium.