Otocinclus Catfish – Complete Guide To Care, Breeding, Tank Size, And Diseases

The otocinclus, also known as the otocinclus catfish from the Loricariidae family are a species of freshwater catfish indigenous to South America. They are also referred to as otto fish or ottos fish or with the spelling variation of oto fish. They also have an unofficial name called “dwarf suckers”. This has to do with their sucker-shaped mouths designed for them to feed on algae.

Since they are algae eaters, they are often added to a freshwater aquarium to help clean up the tank. Another amazing thing about the otocinclus is it’s a relatively low maintenance fish. Low maintenance usually equates to easy care and a suitable species for beginner aquarists. Otocinclus catfish like to dwell at the bottom of the aquarium so they are creatures that are easily hidden. Thanks to their markings, they can also easily blend in with the substrate.

Otocinclus Catfish: A Quick Overview

Otocinclus catfish are small, peaceful fish that are commonly kept in aquariums. They are known for their ability to help maintain clean, clear water by eating algae and detritus. Otocinclus catfish prefer a well-planted aquarium with plenty of hiding places and a temperature range of 72-82°F.

Information ChartOtocinclus Catfish
Care Level: Easy
Temperament: Peaceful
Color: Various colors
Lifespan: 3-5 years
Size: 1-2 inches
Family Loricariidae
Diet: Herbivore
Minimum Tank Size: 10 gallons
Temperature: 75-82 ºF, 24-28 ºC
Water Conditions: Warmer slow flowing water with a neutral pH at about 7
Tank Mate Compatibility Other peaceful fish

Care Level

As said, the otocinclus catfish is relatively easy to care for. They don’t take too much thought and effort and are great for those just looking to dabble in aquarium keeping. For fish that require less care than a lot of other species, they actually decrease your tank maintenance when added to an aquarium.

Otocinclus Catfish Care Guide
Photo by AJC1

Since they are algae eaters, they end up taking care of other fish more than it needs care itself. For them to really thrive, it’s suggested that they are added to stable tank environments where they can get an easy foothold.

Temperament and Behavior

The otocinclus catfish stays closer to the bottom of the tank and keeps out of the way of other tank mates. The catfish otocinclus is considered a very peaceful little fish. Since they are small, they often end up being prey to the larger fish kept in the tank. This contributes to why they are a little bit more skittish than other fish as well.

Due to this, they are excellent runners (or swimmers) and can be very hard to catch. They are algae eaters or tank cleaners, so they spend most of their time on the bottom. When they have cleared that part of the tank from algae, they will migrate to other areas.

These little creatures can also latch on to the side of the tank which is where algae can accumulate as well. When they stick on to the side of the tank, this is when you can get a clear view of their unique markings. Otocinclus catfish also tend to congregate in groups and feed in the same areas.

Otocinclus Catfish Appearance

Otocinclus Appearance

The otocinclus catfish have small sucker mouths that they use to eat algae. They come in different colors and patterns across species. The most common colors include muted green, brown, and gray with a darker horizontal line at the flanks. They are also mistaken as sharks due to their streamlined body shape. 

A fish swimming in water

Description automatically generated with medium confidence

They have a cylinder-shaped body with narrow heads and backs. The armor plating across their bodies shields them from harsh substrates.

Otocinclus Varieties

The otocinclus catfish or catfish otocinclus are from the loricariidae family and are native to South America. They are normally found in freshwater and do well in a freshwater aquarium.

There are many species of otocinclus catfish, with some pretty recently discovered. Since they often fall prey to other fish, the otocinclus sports armored plating across its body.

When we look at the different species, the otocinclus catfish varies in patterns and markings. We will give you a breakdown of each one and its common markings.

Common And Dwarf Otocinclus

These two resemble each other in terms of appearance. They possess a brown speckled body with a white underside. They both also have a dark stripe running down the length of their bodies, with the dwarf otocinclus’s caudal fin being shaped a bit differently.

Golden Otocinclus

Due to their name, the golden otocinclus has more golden hues. If not looked at closely, they can easily be mistaken for a common otocinclus because of the same speckled markings.

Zebra Otocinclus

The zebra otocinclus also takes after its name and its namesake – the zebra. You can see black and white stripes along the length of its body, and the shape and direction of the stripes can also resemble tiger stripes. This is what also earns them the name of Tiger Otos.

Otocinclus Lifespan

These smaller creatures won’t keep you company for as long as you would like, and they typically inhabit the tank for 3-5 years. How long they live in captivity is directly correlated to how they are cared for. If you can provide them with the ideal environment, these algae eaters can live for as long as possible.

Otocinclus Size

We keep mentioning that they are small creatures, and now we will give you an idea of just how small they are. How big do otocinclus get? The adult otocinclus catfish grow to only about 2 inches long. The largest species can be about 2.2 inches, and the smallest ones are only an inch long. They don’t breathe well, making them less suitable for swimming for vast distances.

Otocinclus Natural Habitat And Origin

Otocinclus catfish is native to South America and the small streams of North America and Venezuela. However, they are absent from the lowlands of Amazon and Orinoco.

Streams and small rivers have slow-moving water with plenty of oxygen. The water usually has soft sand and muddy substrate with scraps of tiny rocks. 

Otocinclus Care And Tank Setup

As said, the otocinclus catfish is relatively easy to care for. They don’t take too much thought and effort and are great for those just looking to dabble in aquarium keeping. For fish that require less care than many other species, they actually decrease your tank maintenance when added to an aquarium.

Tank Size And Specification

These cute little catfish are great for smaller tanks. We are talking about 10 gallons small, which is decent for most households. It won’t take up too much space, and with these little algae eaters that are peaceful and require little maintenance, they are a good addition to almost any setup.

Otocinclus Care And Tank Setup

Optimum Tank Size For Otocinclus 

The minimum tank size for an Otocinclus catfish would be around 10-gallons. These fishes have to be kept in groups; otherwise, they can suffer from emotional stress. Groups of three or more fishes will reduce their loneliness and develop their playful nature. For them to really thrive, it’s suggested that they are added to stable tank environments where they can get an easy foothold.

Since they are small creatures, a small tank will do. These fish like to keep to the bottom, and they aren’t big swimmers, which is why a tank size of 10 gallons for a group of 4-6 is ideal.

Tank Shape For Otocinclus 

A rectangular tank shape is the best for Otocinclus fishes as it increases the surface area of the water. Proper gas exchange between air and water ensures the better health of the fish and improves the quality of water in the tank. They can thrive in circular or vertical tanks as well.

Filter Type

Filtration is very important to keep the water in the tank clean and healthy. Otocinclus require purified water for their survival. Water from any RO system is the best for avoiding risks as they are delicate freshwater fishes. Use a canister filter with a GPH rating four times the tank’s volume.

These algae-eating fishes can keep their tanks really clean. Water changes should be done every one or two weeks to eliminate nitrates and ammonia in the tank. 


Since the otocinclus catfish spend most of their time on the bottom of the tank, fine-grained sand is a great substrate to line your tank with. Larger-grained substrates can hurt the otocinclus. Rocks and plants are important because that’s where algae abundantly grow. 

Otocinclus is known as the bottom-dwelling fish. They swim in the lower levels of the tank and feed on the algae. Harsh substrates like gravels and pebbles can hurt their bellies while feeding and cause infections.

How Many Otocinclus Can You Put In A Gallon Tank?

Should Otocinclus be kept in groups? It is advised that they are, they tend to group in nature and feed off algae and perhaps algae wafers in certain spots, and there is no reason why they shouldn’t be given that opportunity in captivity.

Otocinclus do not survive well as a single fish. They can suffer from loneliness and stress, resulting in a fatality. A 10-gallon tank can easily hold 4-6 fish. Remember that the more fish you have, the more gallons you need. Think about increasing the tank size by a few gallons with each fish you add.

Water Parameters For Otocinclus

Water Temperature

The water temperatures would be best between 75-82 degrees Fahrenheit, translating to about 24-28 degrees Celcius. Sudden temperature changes can cause infectious diseases to the fish. You should always keep them in the water temperatures used in the wild. In the aquarium, it’s easier to maintain the ideal tank conditions.

Water Flow Rate

Otocinclus are freshwater fishes who survive in the slow-flowing waters of streams and rivers. The water flow inside the tank should be similar to its natural habitat. Filters with less water current are the best for otocinclus tanks as they will keep the water flow moderately low.

Ph Level

Warmer slow-flowing water with a neutral pH at about 7 is best suited for the otocinclus catfish. It needs to be well oxygenated, so look into that.

Since they are algae eaters, they take care of other fish more than they need to care for themselves.

Water Hardness

Otocinclus do not do well in hard water. Soft Water with a reading of about 15dH is the best.

Otocinclus Catfish Tank Landscape

Best Plants For Otocinclus Plants

The Otocinclus catfish will not eat the plants in the aquarium. They only want to eat the algae growing on the plants. More plants will create more surface area for the growth of algae.

Otocinclus Catfish Tank Landscape

They aren’t called “suckers” for nothing. They tend to be in slow-flowing streams and rivers of fresh water and a domestic tank; they adapt by attaching themselves to rocks and substrates. For this reason, it’s a good idea to make sure your tank is populated with suitable plants and other natural inanimate objects.

Some of the slow-growing plants suitable for Otocinclus are,

  • Java Fern
  • Anubias
  • Echinodorous

Worst Plants For Otocinclus

Plants that grow very fast are harmful to an Otocinclus tank. They consume the carbon dioxide and other nutrients present in the water before the growth of algae.

Decorations For Otocinclus Tank

The aquarium needs to be properly decorated with plenty of hiding spaces. Hiding places can act as shelters when they get tired or stressed. Use large rocks to make cave-like structures for your fish to rest. Softened branches, bogwood, and small round stones can provide your fish with surfaces to graze.

Avoid sharp stones and objects as the Ottos can hurt themselves. An injured fish can contaminate the water in the tank.

Lighting For Otocinclus Plant

There should be plenty of warm lighting to mimic the natural living conditions of the fish. Also, make sure the tank is placed where plenty of sunlight will be streaming through the window.

Feeding Otocinclus Catfish

Best Diet For Otocinclus

The otocinclus catfish are freshwater fish that are considered herbivores. For this reason, you need to make sure whatever food you feed the catfish otocinclus reflects that. Again, they are algae eaters in the wild and are still in captivity. You can look at algae wafers, which make good supplements, as well as fresh veggies you have lying around the house.

Feeding Otocinclus Catfish

Lettuce pieces and spinach are great substitutes for the otocinclus catfish, but make sure you remove any leftover pieces from the soil the water conditions. Blanched vegetables like brussel sprouts and zucchini are suitable supplements in a diet for Otocinclus. Wash them thoroughly to eliminate the insecticides and pesticides present on them.

How Often Should You Feed Your Otocinclus?

It is healthy to feed Otos once every day. Removal of any leftover food from the tank is crucial to maintaining the proper water quality. Keep an eye on the algae growth inside the tank to understand how much extra food you need to give.

Otocinclus Temperament And Behavior

The otocinclus catfish stays closer to the bottom of the tank and keeps out of the way of other tank mates. The catfish otocinclus is considered a very peaceful little fish. Since they are small, they often prey on the larger fish kept in the tank. This contributes to why they are a little bit more skittish than other fish.

Otocinclus Temperament And Behavior

Due to this, they are excellent runners (or swimmers) and can be very hard to catch. They are algae eaters or tank cleaners, so they spend most of their time on the bottom. When they have cleared that part of the tank from algae, they will migrate to other areas.

These little creatures can also latch onto the side of the tank, where algae can accumulate as well. When they stick on to the side of the tank, this is when you can get a clear view of their unique markings. Otocinclus catfish also congregate in groups and feed in the same areas.

Ottos can rise to the surface sometimes to breathe some air. They can absorb oxygen through their gills when they swim to the surface and avoid pumping their buccal cavities at the bottom. If this happens often, take note that your aquarium water lacks sufficient oxygen.

Are Otocinclus Lonely Or Societal In Nature?

Otocinclus do not like staying alone. They can suffer from loneliness and psychological stress. Keeping them in small groups of three or more is the ideal representation of their natural living conditions.

Otocinclus Catfish Tank Mates

An aquarium can look quite sparse and empty with only the otocinclus catfish. They are usually supplemental fish in a tank with many others. How many otocinclus catfish should be kept together? We recommend at least 4-6. Just be sure that your tank is large enough. Aside from other otocinclus catfish, what other fish make good friends?

Otocinclus Catfish Tank Mates

Ideal Tank Mates For Otocinclus

Since they are small and fall prey to other fish, you shouldn’t include any aggressive or predatory species. Fishes that will not fight for food and survive in similar water conditions are your best option. However, the otocinclus catfish can get along quite well with other fish. This is why there is a myriad of choices for roommates such as tetras, boraras, Dwarf Gouramis, rasboras, barbs, mollies, other catfish, and even other algae eaters such as shrimp and snails.

Worst Tank Mates 

Feisty and aggressive fishes should be avoided as tank mates for Otocinclus. Big-mouthed fishes can easily end up eating them as food. Some worst tank mates include cichlids, Oscars, Jack Dempsey, and goldfish.

Breeding Otocinclus Catfish

The otocinclus catfish are not easily bred in captivity, and this is due to their particular needs. The conditions such as the water temperature and things like lighting will also affect your chances. The water should be kept at warmer temperatures anyway (with it being on the warmer side for breeding), so the water condition is the least of your worries. Try increasing the tank’s temperature by at least 10 degrees, around 78℉, to help them breed without difficulty. 

You know breeding is about to happen when the males chase the ladies around the aquarium. Separate this breeding pair and put them in a different tank with the ideal breeding conditions. After this, it will take them at least two weeks to prepare for the mating ritual. The female otocinclus catfish lay eggs around the tank’s surface in small bunches, and the males head over to fertilize them. The incubation period of the otocinclus catfish only takes a few days. After that time, you will have plenty of fry swimming around and increasing the population of your tank.

Ensure that the tank is perfectly prepared to shelter these tiny babies. Keep changing 50% of the water every week, from mating to breeding to finally growing the fry. The breeding tank must have 75-80 liters of water to suitable living conditions for the new fry.

The babies need healthy food as well, and algae and bacteria are the main sources of food. The care level needed for the fry is minimal, and they will soon start looking and eating the same food as the adults.

Otocinclus Breeding Level


Otocinclus Sexual Dimorphism

Otocinclus exhibits very prominent sexual dimorphism. Upon reaching reproductive age, the females become much larger and wider than the males. Their sex organs are also distinctively different. Females have larger and more vibrant sex organs.

Males have genital papilla with several rows of odontoid (modified denticles.) These organs are visible at the side of the tail system. This organ helps orient the Otocinclus male fish during the breeding process. 

Maintenance And Care

Why do my otocinclus keep dying? A lot of people ask that question of these hardy fish. You need to make sure you are taking care of them to the best of your ability. The healthier the aquarium is, the happier your fish will be. They are pretty hardy but can be fragile at the same time.

Adapting to a new environment is the hardest part of caring for the otocinclus catfish, which is why they need to be introduced carefully. The food you feed them needs to reflect their natural diet (consisting mainly of algae and plants), and the aquarium conditions need to be ideal.

Since algae are their main food source, make sure you don’t completely wipe it out when cleaning your aquarium. The otocinclus catfish is a freshwater fish, and like most other freshwater fish, they are susceptible to sudden water changes. Due to their small size, these fish cannot bear too much movement in the water.

If you happen to have sick fish, make sure you quarantine them away from the rest of the group quickly to prevent the spread of the disease.

Otocinclus Catfish Diseases:

The otocinclus catfish is luckily free of many diseases, but they can develop fungus (not a surprise for most freshwater fish in an aquarium.) The two most important factors are a clean aquarium and healthy food. Once you start noticing a lack of appetite, wounds, color changes, and decreased activity, you know your fish isn’t doing so well.

Otocinclus are host to several harmful diseases. Some of them are,

Cotton Mold

The fungus Saprolegnia is the cause of this parasite infection. Small, fluffy growth can appear on the fins and bodies of the fish. This infection can cause an acute psychological imbalance in the infected fish.

The fungus can worsen the mineral salt and water regulation in the fish resulting in death. Lethargy, unusual swimming patterns, and respiratory problems are other symptoms.

Treat this disease with substances like malachite green, copper sulfate, hydrogen peroxide, and formalin. 

White Spot Disease

This is the most common freshwater disease that also affects Otocinclus. White spots that mirror the activities of protozoans start appearing on the body and gills of the fish. 

Visible symptoms include irritation and inflammation in the infected fish. You may find it scratching itself against coarse surfaces in the tank. Breathing troubles, lack of hunger, and reclusiveness can also be symptoms of this disease. 

To treat this disease, you have to increase the temperature of the water and take it above 30℃. Try adding aquarium salt in the water to increase the temperature as well. Other fitting treatments would be the use of formalin and machete green.

Gold Dust Disease

The parasite causing the disease affects the gills and skin of the fish. Dusty yellow spots start appearing all over the body of the infected fish. This causes so much irritation that excessive scratching against hard surfaces can eventually erode the fish’s skin. 

Lethargy, lack of appetite, labored breathing, and fast gill movements are other symptoms of the disease. Acriflavine, methylene blue, and copper sulfate can improve the condition of Gold Dust disease.


Roundworms can cause total organ failure in Otocinclus. Poor water conditions in the tank are significant causes that contribute to the growth of roundworms in the tank. These worms can be seen sticking out of the anus of the infected fish, and considerable shrinkage of the belly is spotted. 

Mix levamisole and parachlorometaxylenol in the fish tank’s water to treat the diseases. 

Facts About Otocinclus

  • Otocinclus are excellent algae eaters. They help to keep the fish tank clean. They help other fishes by improving the water conditions inside the tank. 
  • Otocinclus are dwarf-suckers due to their tiny size and narrow, pointed mouth.
  • They are native to the freshwater streams of North America and Venezuela.
  • The smallest Octacinclus available is only about an inch long.
  • These fishes cannot survive alone without their friends in the tank. They can suffer from loneliness and stress if kept alone. It is safe to keep them in groups of 5-6 in a 10-gallon tank.
  • They are peaceful fishes that can stay with countless other tank mates.
  • Their average lifespan is about 3-5 years in the best living conditions inside a tank.
  • They can sometimes stick to the sides of the tank. This is when you can see their dark horizontal stripe at the flank and their sucking-mouth.
  • Otocinclus do not eat live plants, but they feed on the algae that grow on them.
  • They come in three varieties – Dwarf Otocinclus, Golden Otocinclus, and Zebra Otocinclus. 
  • The female Otocinclus looks distinctively different from the males. They are larger and wider in appearance.
  • Breeding Otocinclus is very difficult. The perfect temperature and lighting needed to breed are quite hard to obtain inside a fish tank.


How Many Otocinclus Should Be Kept Together?

Otocinclus must be kept in small 5-6 fishes in a 10-gallon tank. You can keep adding more fish by increasing the capacity of your tank. These fishes do not like to stay alone, suffering from loneliness. Do not keep them without their companions. 

Does Otocinclus Produce A Lot Of Waste?

Yes, Otocinclus produces a lot of waste as adults. They are algae-eating omnivores who can have vast amounts of waste. They can destroy a planted tank in minutes. 

Do I Need To Feed Otocinclus?

Yes, you can give some supplementary food to Otocinclus. They eat algae present on the surface of plants and objects in the tank. Fresh vegetables like lettuce and zucchini are also good for them. 

Does Otocinclus Clean Glass?

Yes, Otocinclus clean glass. However, they feed upon algae present in the tank. Algae is accumulated chiefly on the plants, and they love cleaning the plants more than the glass.


The otocinclus catfish are handy little pets to keep around. They are smaller in size compared to other catfish and like to swell at the bottom of the tank. However, much like most other catfish species, the otocinclus catfish is peaceful and can get along well with other tank mates. Not to mention their handy role in keeping the aquarium clean. They can save you the trouble of feeding them regularly with the natural buildup of algae in the tank.

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