April 3

Otocinclus Catfish Aquarium Care Guide


Otocinclus Catfish

The catfish group consists of many unique species, and among these, is the Otocinclus genus. Otocinclus catfish are found in abundance in the shallow waters of South America –  from Argentina to Colombia, Brazil, Peru, Venezuela, and Paraguay.

There are about 19 different species in this genus, and these are primarily distinguishable by their colors. They are known by several monikers such as dwarf suckers,otos, dwarf sucker-mouths, and cats to mention but a few.

Some of the most commonly kept otocinclus fish in the home aquarium include:

  • Otocinclusvittatus: these are speckled brown colorations all around the body with the underside being white. There is a dark brown stripe that runs laterally along the mid-region of their body – from the head to the tail.
  • Otocinclus macrospilus: often called ‘dwarf oto‘, this species has a brown body and a small dark patch that intersect the rear end and the tail line. It is also known to possess an eardrum-like structure.
  • Otocincluscocama: These are distinctive for the black-and-white-striped blotches spread all over their body, and it is for this reason they are called zebra otos‘. Furthermore, their lateral line runs right from the tip of the head to the very end of the tail.
  • Otocinclusvestitus: This species bears some similarities with O. macrospilus, but its (O. vestitus) lateral line is rather thin. Additionally, the body is typically grey while the lateral line is dark brown.

On the appearance and body outline; the body of otocinclus fish is generally elongated, and it widens around the center while narrowing towards the head and the tail. They also have a row of bones over their body. They can only grow to a length of about 5 cm over a 3 – 5-year lifespan.

They also possess transparent fins and a tough cupule-shaped mouth which is of immeasurable benefits to them when sourcing for food on the substrate.

Otocinclus Catfish Behavior

Apart from their appearance, the very first thing you, as an aquarist, will desire to know about any fish is the behavioral pattern. And for this particular kind of fish; what you will get to observe is that they are easy-going aquatic creatures that will not have any problem with their neighbors in the tank. Plus, they are also undemanding so, you should have little or no trouble keeping them – this is why beginners will love to have them.

 Another interesting point to take note of is that they are a schooling type of fish, and will do well in a group of 4 – 5. Although they may not appear to be very fast swimmers, they exhibit sharp reflex which is observable whenever they make quick darts away from danger.

They like to stay at the bottom of the tank but would seldom venture to the surface to get atmospheric oxygen- this could be very crucial whenever there is a short supply of dissolved oxygen in the tank. And it is worth mentioning that you should not hesitate to correct the situation at the very instant you noticed such a change in their orientation.

Otocinclus Catfish Feeding

The number one food otocinclus love to take is soft green algae; this is why they are often referred to as great tank cleaners‘. They will readily scrape the surfaces within the aquarium to obtain the algae present thereon. Besides the naturally growing algae, you can also provide them with algae wafers.

Furthermore,otocinclus fish portray herbivorous feeding inclination, which means you can feed them with vegetables such as courgette, lettuce, spinach, and squash. These should be chopped into bits before making them available for the ottos in the tank.

Optionally, you can boil the vegetable for some minutes – say 2 – 3 minutes – and then put [the boiled vegetable] into the tank ensuring that it stays at the bottom of the tank where the fish can easily reach the food. You can actualize this by holding the vegetable down with a rock. You should rid the tank of any leftover (food) after 24 hours.

Be mindful of the fact that otocinclus catfish do not cherish eating old algae – they usually prefer it fresh or not-so-old. By the way; you should not rely on them to clear all the algae that may be present in an old tank. Another thing is that you should always adequately supplement their diet – do not leave them to only consume the algae that are naturally growing in the tank.

Otocinclus Catfish Care

Caring for the otocinclus catfish should not portend any major challenge as they are easy to keep – although O.affiniscould prove to be pretty demanding. All you have to ensure is that they are fed with a healthy diet – it is often posited that the fattest ottos are the healthier ones – and, that good hygiene is maintained in their tank.

Owing to this statement above, you will need to regularly check the levels of ammonia and nitrite in the water, and also prevent the build-up of these substances. Again, the water chemistry – pH level temperature range and oxygen level – should be effectively monitored. This is the more reason you will have to get measuring devices available in the home.

Additionally, your intervention may be required to clear excessive algal mass out of the aquarium; they may be predisposed to some diseases when left to inhabit a tank ladened with algae. A 25% water change should be carried out every week.

     Otocinclus Catfish Tank set-up

    To avoid putting the cart before the horse, and for the fact that they are bottom-dwellers, it is important that we start setting up the tank for otocinclus right from the lower level by setting a substrate of finely grained sand – this is similar to what is obtainable in their natural habitat. Having done that, you should furnish the tank with rocks and provide a lot of hiding places for the fish therein.

    Additionally, plants should be adequately provided in the tank as they love to dwell in densely vegetated waters. Plants such as Cryptocoryne, Java fern, Anubis, Java moss, and Cabomba should be fitting in this regard. Wooden roots and bogwood will also make a great addition to their tank.

    Despite their small size; the otocinclus fish still need some good space to thrive and live their life to the fullest. In this wise, a 38-liter tank should be good enough for housing a shoal of 5 – 6 otocinclus fish. The size of the tank can be increased for every other to added after that.

    The tank should also be equipped which highly functional filtration system that can appropriately recycle water for about three to four times daily; this will help put the concentrations of ammonia, nitrite and nitrate in check, and also ensure an adequate supply of dissolved oxygen. The tank’s lighting system can be moderate or normal – otocinclus are pretty active during the day.

    Water parameters

    As you ensure that the quality of water is not compromised, you should also not lose cognizance of the need to keep the water chemistry within the normal range. The reason is that fluctuations and/or sharp changes in water chemistry may stress the fish and cause them health issues. Therefore, the following parameters should be strictly adhered to:

    • Water temperature: 22°C – 26°C is the perfect temperature range for otocinclus fish.
    • pH range: Otocinclus fish need slightly acidic to moderately alkaline water – pH value of 6.0 – 7.5 – to survive.
    • Water hardness: The ideal water hardness degree for otos is between 5dH – 15dH; that is, moderately soft to moderately hard water.

    Aquarium mates

    On their part, they have got no issue staying in the same tank with other fishes, but due to their relatively small size, they are vulnerable to attacks from other species especially the aggressive and/or bigger fishes. As such, you have to exercise some care when selecting tankmates for otocinclus fish. In this view, goldfish, Oscars and cichlids should not be put in the same tank as them.

    Some of the regular or good neighbors you can put up with otocinclus fish include danios, guppies, harlequin rasboras and corydoras. Besides these, other invertebrates like mystery snails, rabbit snails, ramshorn snails, red cherry shrimp, bamboo shrimps and some other ones can be added to the community tank housing otocinclus.

    Otocinclus Catfish Breeding

    While taking care of otocinclus catfish may be less intensive, breeding them comes with a lot of challenges, and for this reason, many aquarists do not attempt to breed the fish in the home aquarium. But should you desire to give it a try, you will find the following piece of information quite valuable.

    As with any other fish, the first thing to do prior to the breeding proper is to distinguish between the male and female otocinclus fish – this is however where the difficulty begins; it is not easy to sex them. Notwithstanding, the female otos are typically broader and plumper than male otos. Apart from the variation in size; male otos can be distinguished [from female otos] for the genital papilla – an organ that serves some reproductive purpose, and it is usually seen around the tail region – they possess.

    With the sex differences sorted out, you should separate the male and female oto into different tanks or tank compartments where they will be fed in preparation for spawning. This can take between one to two weeks.

    They should be given a diet that is rich in protein- for instance, live feeds like daphnia and/or brine shrimp – along with algae wafers. The success of this conditioning will eventually be reflected in the sizes of the fish, even as the belly of the female oto is expected to become fuller.

    The temperature within the breeding tank should be set at 26°C, and the tank should be furnished with an adequate amount of plants as this could be useful for holding the cluster of eggs that will be laid.

    The male and female otos should then be brought into the same tank for spawning to take effect. As a sign of its readiness to spawn, the male will be seen chasing after the female oto and subsequently catches up with her to mate in a T-shaped position. As a consequence of this action, the female gets to move her eggs to the abdominal region.

    The female oto then swims to the spot or substrate where she lays her eggs with the male following after her. The mating process [and egg-laying] continues until all the eggs are laid. Otocinclus fish can lay up to 50 eggs during a spawning session.

    The eggs are fertilized by the sperm released by the male and are left sticking to the leaves or surfaces on which they had been laid. So, in essence, otocinclus fish do not portray a reputable parental instinct as you will see in some other classes of fish.

    The eggs should hatch after a couple of days, and you will get to see the fry swimming around to start sourcing for their favorite food, algae, as well as some other microbes that may be present in the aquarium.

    NOTE: You should take heed to ensure that the water in the breeding tank is always clean; you can do a 50% water change every week while the breeding process lasts. Plus, you should also consider having a tank with a capacity of about 75 – 80 liters – or one that will be large enough to accommodate them – as a breeding tank.


    Though no known disease is particular to otocinclus catfish, they are prone to a host of diseased conditions nonetheless. And some of these diseases are now discussed:

    1. Cotton mold: Cotton mold is a parasitic infection caused by a fungus known as Saprolegnia.  The disease is also known as saprolegniasis. Infected fish is observable to have fluffy, cotton-like growth appearing on its fins, gills, and body.

    The disease is capable of causing several physiological disturbances to the infected fish. It can adversely affect the regulation of mineral salts and water in the fish – a situation that could be terminal on its own. Furthermore, the skin and fin become necrotic, and the fish gets lethargic and may move in an uncoordinated fashion. Respiratory complications may also occur.

    The rate of saprolegniasis-related mortality is quite high – prevention remains the best bet – but treatments [using substances such as malachite green, copper sulfate, sodium chloride, hydrogen peroxide, and formalin] have brought about significant improvement.

    • White spot disease: Arguably the most common infectious disease tormenting freshwater fishes, and otocinclus is not left out. The onset of this disease comes with the appearance of a white spot on the body and gills of the fish. These spots are a reflection of the activities of protozoans. The spread of this disease may be exacerbated by a sharp/sudden drop in temperature.

    Fish affected by this disease are seen rubbing their body against surfaces as though feeling irritation and do experience difficulty in breathing – whereby you will see them gasping for breath. They may also not eat like they usually do, and they may become reclusive.

    Treatment course using high temperature – above 300C – plus aquarium salt is the most economical way of getting rid of white spot disease. But since otos cannot survive at such a temperature, it is fitting that other (treatment) options such as formalin or malachite green should be utilized.

    • Gold dust disease: The parasite responsible for gold dust disease normally attaches itself to the gills and skin of its victim, and infected fish are observed with dusty yellow spots on their body. The skin of the fish could eventually erode as it rubs against hard objects. Lethargy, rapid movement of gills, loss of appetite, and labored breathing are some other signs that may become pronounced in due time.

    Formulations such as acriflavine, methylene blue, malachite green, and copper sulfate can be used in taking care of this condition.

    • Roundworms: Roundworms are also capable of causing an array of organ dysfunction in otos. They are rather stubborn and may resist treatment to some extent. Poor water quality is one of the factors that advance their proliferation in the aquarium.

    These worms can be seen protruding from the anus of their host, and will likely cause the belly to appear as though it were shrinking. Lethargy and appetite loss are two common signs that evolve with roundworm infections.

    To treat this infection; you can feed your fish with feeds soaked with thiabendazole or mix levimasole or parachlorometaxylenol with the water in the aquarium.

    One could go n discussing the many diseases that may disturb the well-being of your oto cats, but for want of time, it’s ideal I stop here. However, it is important to stress that prevention is better than cure, and in this case, the need to maintain a highly hygienic environment in the aquarium cannot be overemphasized.

    Again, you should always look out for any change in behavior from your pet and ensure that they are fed with a balanced diet. Plus, do not neglect any symptoms that may occur on the fish’s body.


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