Otocinclus care guide

Plan a tank with otocinclusSee all tank mates

Otocinclus quick facts

Tank setup

A group of six needs at least a 20-gallon (76 L) tank. Only add them to a mature tank, a few months old, with plenty of plants, driftwood and smooth rocks that grow algae and biofilm. Gentle to moderate flow and good oxygen suit them. Put a sponge over the filter intake, as they are very small.

How many otocinclus in a tank?

The smallest common tank that suits otocinclus is a 20 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.

Water parameters

Aim for 21–26°C (70–79°F), pH 6.0–7.5 and soft to moderately hard water. Otos react badly to ammonia, nitrite and high nitrate, so keep the water clean and stable. Small, regular water changes are better than big, sudden ones.

Best tank mates for otocinclus

These popular species share otocinclus' water needs and temperament. See the full list of 102 good matches.

• Betta fish

  6.5 cm (2.6 in) · 24–28°C (75–82°F)

• Cherry shrimp

  3 cm (1.2 in) · 20–27°C (68–81°F)

• Nerite snail

  2.5 cm (1 in) · 22–27°C (72–81°F)

• Guppy

  5 cm (2 in) · 22–27°C (72–81°F)

• Dwarf gourami

  7.5 cm (3 in) · 24–28°C (75–82°F)

• Neon tetra

  3.5 cm (1.4 in) · 21–25°C (70–77°F)

• Panda corydoras

  4.5 cm (1.8 in) · 21–25°C (70–77°F)

• Bristlenose pleco

  12 cm (4.7 in) · 22–26°C (72–79°F)

Avoid keeping otocinclus with

• Angelfish: Angelfish can eat otocinclus: they're small enough to fit in its mouth once it's grown.
• Common goldfish: Common goldfish can eat otocinclus: they're small enough to fit in its mouth once it's grown.
• Oscar: Oscar can eat otocinclus: they're small enough to fit in its mouth once it's grown.
• Bala shark: Bala shark can eat otocinclus: they're small enough to fit in its mouth once it's grown.
• Chinese algae eater: Chinese algae eater is aggressive and will bully or injure peaceful otocinclus.
• Convict cichlid: Convict cichlid can eat otocinclus: they're small enough to fit in its mouth once it's grown.

Feeding

Otos are herbivores that live on soft algae and biofilm, and many ignore flakes and pellets. Offer algae wafers, blanched zucchini or green beans, and gel food spread on a rock. Driftwood and dried leaves grow extra biofilm to graze. A well-fed oto has a rounded belly; a sunken belly means it is starving.

Behavior

Very peaceful and a little shy. They feel safest in a group of six or more and often graze side by side. Good tankmates are small, calm fish such as tetras, rasboras and small corydoras, plus dwarf shrimp and snails. Large or pushy fish can stop them from feeding.

Breeding

Most otos are still wild-caught, but they do spawn in aquariums now and then. Females are larger and broader than males. They spawn in a T-position like corydoras and stick small eggs on plants and glass, often after a large, cool water change. The tiny fry need constant algae, biofilm and very fine foods.

Tips from experienced keepers

• Buy only otos with rounded bellies. Many arrive starved after shipping, and thin ones rarely recover.
• Add them to a tank that has been running for at least 3 months so there is algae and biofilm to graze.
• Most losses happen in the first few weeks. Feed vegetables or algae wafers from day one.
• Leave some algae on the back glass, rocks and wood as natural grazing.
• Keep them away from large or boisterous fish that hog food or bully them.

Sources

We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.

• seriouslyfish.com
• fishbase.se
• aquariumcoop.com
• scotcat.com
• fishkeepingworld.com