rm
Passport
- Family
- Bristlenose Catfish
- Grows to
- 3.5 cm (1.4")
- Lives
- 3–5 years
- Temperament
- Peaceful
- Care
- Intermediate
- Swims
- On the bottom
- Keep
- In a group of 6 or more
- Water
- 21–26 °C (70–79 °F)
Peru
Care requirements
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On record for Otocinclus: adult size, lifespan, minimum tank, temperature, ph, hardness, minimum group, diet, care level, swim level, tank length.
A figure that is not on record is left out rather than guessed. One marked Suggested comes from keeping knowledge rather than a page.
- Minimum tank 57 L / 15.0 US gal
- pH 5.5–7.5
- Hardness 1–12 dGH
- Diet algae grazer
- Tank length 45 cm minimum
Care notes written from general aquarium knowledge, not from the cited sources.
About
Otos are the best algae eater you can put in a small planted tank, and the one most likely to die in the first fortnight. Both halves of that are worth knowing before you buy any.
They're tiny suckermouth catfish that graze soft green and brown algae off leaves and glass without damaging a thing — they'll clean a plant that no other algae eater can work on, and they do it delicately enough for the most fragile species.
Almost every oto in the trade is wild-caught, and many arrive starved after weeks in the supply chain with nothing to graze. That, rather than anything about your tank, is why they have such a reputation for dying inexplicably.
Tank setup
Only add otos to a mature tank with visible algae growing in it. This is the whole game. A new tank, or a spotless one, has nothing for them and they starve while looking fine.
Give them broad surfaces to graze: plant leaves, wood, glass, smooth stone. They spend their day working over them.
Keep them in a group. They're social, they graze together, and singles are noticeably more nervous.
Keep the water clean and well oxygenated, with gentle flow. A sponge filter suits them, and they're less tolerant of poor water than most catfish.
Buy the fattest ones in the shop tank. A hollow-bellied oto is already in trouble.
Feeding
Otos eat soft algae and biofilm, and that must be genuinely available before they arrive.
Supplement from day one rather than waiting. Blanched courgette, cucumber and spinach are taken readily, and a good algae wafer helps — but they often ignore prepared food at first, so real algae has to carry them.
Grow spare algae if the tank is clean. A jar of stones on a windowsill greening up in the sun, rotated into the tank, is the standard trick and it works.
Avoid: adding them to control an algae problem you're about to fix. Once the algae goes, so do the otos.
Filtration and flow
Gentle flow and good oxygenation. A sponge filter gives both, and they're more demanding about oxygen than their size suggests.
Filter well but leave the algae alone. A tank scrubbed spotless every week is a tank that starves them.
Guard intakes. They're small, and they will investigate.
With plants
Otos are completely safe with plants and are actively good for them, grazing algae off leaf surfaces that would otherwise be smothered.
They'll rasp at a dying leaf, which people mistake for damage. A leaf being stripped was already lost.
A heavily planted tank is the right home for them: more grazing surface, more stable water, more cover.
Health
Most losses happen in the first two weeks and trace back to starvation and stress before purchase rather than to anything you did.
Look at the belly daily. A healthy oto is round-bellied; a flat or concave one is starving and needs food it will actually eat, quickly.
Copper is the clear no. Otherwise check the label for catfish restrictions and respect them, and bear in mind these fish often arrive carrying something already — quarantine does more for them than any bottle will.
Breeding
Otos breed in home tanks occasionally, and almost always by accident in a heavily planted, well-fed, mature setup.
The pattern reported is much like a cory's: the female places small clusters of eggs on leaves and glass, and the adults show no interest in them afterwards.
Deliberate breeding is rare and unreliable, which is why the trade still depends on wild collection. Cool water changes and heavy feeding on vegetable matter are the conditions most often associated with it.
Tank mates
Avoid8
- Chinese Algae Eater Chinese Algae Eater is aggressive and Otocinclus is peaceful and easily intimidated.
- Convict Cichlid Convict Cichlid grows to 15 cm against Otocinclus at 4 cm, big enough to eat it.
- Jewel Cichlid Jewel Cichlid grows to 15 cm against Otocinclus at 4 cm, big enough to eat it.
- Panda Garra Panda Garra grows to 9 cm against Otocinclus at 4 cm, big enough to eat it.
- Pictus Catfish Pictus Catfish grows to 12 cm against Otocinclus at 4 cm, big enough to eat it.
Only with care17
- Assassin Snail Otocinclus is a risk to Assassin Snail: bristlenose catfish and snails are a pairing to watch.
- Bladder Snail Otocinclus is a risk to Bladder Snail: bristlenose catfish and snails are a pairing to watch.
- Clown Loach Clown Loach is a risk to Otocinclus: bristlenose catfish and loaches and botia are a pairing to watch.
- Demasoni Cichlid Demasoni Cichlid is a risk to Otocinclus: african cichlids and bristlenose catfish are a pairing to watch.
- Dwarf Chain Loach Dwarf Chain Loach is a risk to Otocinclus: bristlenose catfish and loaches and botia are a pairing to watch.
No conflict is recorded with the other 80 species in the database, so nothing to flag. 3 species are not covered at all, so they could not be judged either way.