Otocinclus Catfish – Habitat, Care, Feeding, Tank Size, Breeding

The Otocinclus Catfish are active algae eaters, and will, therefore, make excellent cleaner groups to any aquarium. They require a well-established tank, and it is common for them to die upon being introduced to a new setup.

There are around 19 different species in this genus that are distinguished by their colors.


This fish is quite small, and it typically attains a length of 1 ½- 2 inches when mature. It has an elongated body that narrows towards the caudal fin and the head. The patterns and colors differ from species to species.

The common Otocinclus is the most widespread species, and it has a speckled brown body with a white coloration at the bottom part. There is a brown stripe that runs along the side, from the head to the caudal fin, while the rest of the fins are almost transparent. The females are typically broader and larger, although this is more apparent when looking from below or above.


Otocinclus catfish populations are indigenous to the Andes of South America. They have been recorded across Argentina to Colombia, as well as in Paraguay, Venezuela, Peru, and Brazil.

The fish attach themselves to the rocks or substrates of shallow waters in these regions in search of algae. They prefer to school on the riverbanks since the water is calm.

The waters in these habitats are well-oxygenated and neutral, and the fish have access to a lot of light. The fish are capable of breathing air, and they can survive below the water surface without circulating air through gills.


The primary source of food for the Otocinclus Catfish is algae, and you will need to encourage algal growth in your tank. You can achieve this by leaving the aquarium lights on for more than 12 hours and intentionally growing algae on filter media and decorations. If you intend to grow your own algae for the pets, keep in mind that it will take months to get sufficient algae.

Some aquarists will supplement the algae with fresh-steamed veggies like spinach, lettuce, and zucchini, while others offer frozen blood worm, flakes, and spirulina.

Give these supplements to the fish once a week and at night, but remove the leftovers after two days. The food should be placed at the tank’s bottom to make it accessible to the Otocinclus Catfish.

Water & Tank Requirements

Below you can find the water requirements and tank conditions that otocinclus catfish need:

Tank Size

It is advisable to start your Otocinclus Catfish with a 20-gallon tank. You can comfortably keep four to six of the pets in such a setup without worrying about food availability. While some forums recommend keeping up to 10 of them in this tank size, feeding the fish will become hectic for you.

PH and Temperature

The temperature range should be 72-79 °F and 6.8 to 7.5 for PH. The Otocinclus Catfish thrives in soft water, and you should ensure the water’s hardness is kept below 15dH.

Water Conditions

Otos require an established and mature aquarium to thrive, and they are often not recommended for beginners. The levels of nitrites and ammonia should be at 0 ppm, and nitrates should be similarly low. The fish are quite sensitive and intolerable to water pollution, so your tank’s parameters need to be stable.

You will require an effective filter to keep the aquarium habitable for your Otos. Canister and hang-on-back filters are often recommended to keep tanks free of ammonia and nitrites. Renew 30% of the water every week when cleaning the aquarium.


The Otocinclus Catfish is a bottom-dweller and will require a suitable bottom to thrive. A finely-grained sand substrate will mimic the pet’s natural habitat since a coarse substrate can injure their bodies and cause health complications.

The fish will appreciate different types of decorations, including rocks, bogwood, and wooden roots. Ceramic tubes will provide hiding spaces. When it comes to plants, you should opt for slow-growing species since fast-growing ones will use up a lot of CO2 and dissolved nutrients and leave little for the algae. Invest in plants like the Java fern, Java Moss, Anubias, and Cryptocoryne.

You should encourage the growth of algae and refrain from using algae scrubbers.


The Otocinclus Catfish is peaceful and calm and will thrive with other peaceful species. You should keep at least four of the pets together as long as the tank is large enough. Since the pets are small, they dart quickly around the tank. Otos are social pets, and you need to keep them in a shoal. The fish are quite active in the day, where they can be seen feeding on algae on the rocks and decorations.

You can keep the pets with Guppies, Dwarf Gourami, Danios, Tetras, Zebra Loaches, Angelfish, Corydoras Catfish, Harlequin Rasbora, Mollies, and Cherry Barbs. You can also couple Otos with snails and shrimps. Do not keep the Otocinclus Catfish with catfish and large cichlids.


Breeding the Otocinclus Catfish is more challenging than rearing them. Most aquarists refrain from breeding the fish all together, but it is possible with proper care.

The first step is distinguishing between the male and female Otos. The females are plumper and broader than the males who have the genital papilla in the tail region. The next step is keeping the two genders in separate tanks set at 26 °C to prepare them for spawning.

Give them protein-rich foods and algae wafers. The breeding tank should be subjected to 50% water changes weekly to keep it clean. The tank should also have a preferable capacity of 75 to 80 liters.

During breeding, the female Oto chases the female and mates with her in a T-shaped position. The eggs of the female subsequently move into the abdominal region, after which they are laid in the substrate.

This process continues, and can result in about 50 eggs per session. After fertilization by the males, the eggs will be left sticking onto the surfaces where they were laid. It takes a few days for the eggs to hatch, and the fry begin swimming around in search of algae.


Otos will make peaceful additions to any freshwater tank and can be coupled with similarly calm fish like guppies, tetras, mollies, and Zebra Loaches. They demand an established tank, meaning that your setup should be well-cycled and stable before adding them. Overall, Otos are delightful pets to keep.

Updated: February 19, 2020

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