Otocinclus Minimum Tank Size? {Is a 10 Gallon Tank OK?}

How many Otocinclus would you like to keep? Do you want to know how to keep them thriving in the right size tank? In this article, we’ll talk about the minimum tank size and ideal tank details for the Otocinclus.

Otocinclus Minimum Tank Size? 10 Gallons is a starting point for 3-6 Otocinclus, but 20 Gallons is better. Making sure they don’t run out of algae or other food sources in a smaller tank will be difficult. Allow your Otocinclus to shoal in groups of 3-15 in tank sizes starting from 20 gallons and up for better health and quality of living. 

How Many Otos Are In A 10-Gallon Tank?

There are many details that matter more than just tank size. You will be told that a 10 gallon tank could hold 3-6 Otocinclus, but what else is there to consider?

  • Tank setup
  • Distribution of water
  • Tankmates
  • Plants
  • Filtration
  • Heat
  • Food sources

Tank Setup

The tank has to be cycled and ammonia/nitrites need to be eliminated to show 0 ppm on your most recent water test. The first 24 hours will be hard on your Otocinclus. Drip acclimation, planted areas, decorations and a sandy substrate are all recommended.

Distribution of Water

A 20 gallon or 10 gallon tank could be the conventional models of tanks that are most common. It’s better to opt for a longer or wider tank with more footprint instead of only thinking about volume. Spread the 10-20 gallons out over a longer and wider distance and you’ll have more space for your bottom-dwelling Otocinclus to graze and explore.


Ideally, you’re looking to keep 3-6 Otocinclus alone in a 10 gallon tank. They are also peaceful and welcome additions to community tanks. Oscar fish or cichlids may try some aggressive moves to enforce their territories, but your Otocinclus will not compete. They will retreat or stay busy on the glass, rocks or within the planted areas.

Here’s a list of tankmates we enjoy with Otocinclus:

  • Harlequin Rasbora
  • Dwarf Gourami
  • Zebra Loaches
  • Cherry Barbs
  • Tetras
  • Mollies
  • Guppies


The plants you place will provide oxygenation in spaces where they are most likely to rest or hide in. Plants create comfort and assurance that there is always something to nibble on. The following plants work well with your Otocinclus:

  • Anubius
  • Cabomba 
  • Cryptocorynes
  • Echinodorus
  • Java Fern
  • Java moss

Filters and Heaters

A filter is a must, but a heater may not be if you can mimic their tropical climate between 72-82°F (22-28°C). The range is high, but the change should be gradual. A heating guard is important to prevent your Otocinclus from sucking on the heating tubes. Filters need a moderate flowrate to aerate the tank and distribute the dissolved oxygen.

Food Sources

Will there be enough algae in a 10 gallon tank for your 3-6 Otocinclus? If the algae is insufficient, it’s best to train your Otocinclus to eat more leafy greens, cucumbers, bell peppers and algae wafers. The larger the tank, the more space and possibilities open up for your Otocinclus to roam, work, graze and hide when they feel like it.

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How Many Otos Are In a 20 Gallon Tank?

The best part about Otocinclus may not be that they clean the algae in your tank. It gets better when you see them in groups as the best possible version of peace and social living.

They shoal for comfort, fear and stress. They help each other mimic their natural environment where they swim in huge numbers. A 20 Gallon tank would house 3-15 Otocinclus. It’s best to start with a minimum of 3 for shoaling and stress relief.

Add more as you see fit. Stop when you reach a number as high as 12-15 Otocinclus. Test your water and make sure there’s enough algae or other food sources. Acclimate them slowly.

What’s The Ideal Tank For Otocinclus?

An ideal tank would have at least:

  • 6 Otocinclus
  • 20 Gallons
  • 3 densely planted areas
  • 2-3 decorations
  • 2-3 rocks
  • sandy substrate
  • partial sunlight 
  • plenty of vegetables and algae
  • no aggressive tankmates

20 Gallons Or More

Add up to 12-15 depending on how many tankmates there are in a 20 gallon or larger tank. The planted areas will keep them comfortable, provide some nutrients and dissolved oxygen.

Rocks, Decorations and Substrate

The rocks and decorations are additional spaces where algae could also grow for your Otocinclus to graze on. The sandy substrate is safer for their scaless bodies and constant rummaging at the bottom of the tank.


Sunlight will help with more algae growth, but your Otocinclus will also enjoy staying in the shade. They are not nocturnal catfish, but are certainly active at night when the rest of the tank is calm.

Aggressive Tankmates

Aggression at the bottom of the tank will cause your Otocinclus stress. They may stop eating and hide constantly. If you notice that their bellies are sunken in, they are not eating enough. Choose top and mid level swimmers. The bottom level is welcome to peaceful corydoras and larger Amano shrimp.

Is There Enough Algae In A 10 Gallon Tank With Otos?

Your Otocinclus was most likely caught from the wild and not bred. These bottom dwellers are accustomed to eating algae off surfaces. A rock is a great item to place in a tank to attract algae. Your Otocinclus will enjoy the space. Driftwood also works well.

The Algae Rock Trick

  1. Find smooth, flat rocks.
  2. Place them in a container.
  3. Direct the sunlight at them.
  4. Let the algae grow. 
  5. Rotate the rocks in and out of the tank.

When you notice that algae is running low in the tank, your Otocinclus and filter are doing a great job. Take out the clean rocks and rotate in some rocks from your container that are full of algae.


10 gallon tanks can hold 3-6 Otocinclus catfish. They will be more comfortable in groups with more space to shoal, graze and explore. A 20 gallon tank with more planted areas, sandy substrate and enough food to eat will keep your Otocinclus happier and healthier.


Thanks for visiting HelpUsFish.com for another article on Otocinclus that we greatly enjoy in our community tanks. Check out more of our articles on the variety of marine life we research and keep. Bye for now!

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.