Otocinclus catfish
Otocinclus vittatus
intermediate careOverview
The otocinclus catfish (Otocinclus vittatus), or “oto”, is a tiny, peaceful algae-grazer that is superb at keeping soft green algae off leaves and glass. It is also genuinely sensitive: many arrive from the shop weakened and underfed, and all of them depend on the natural algae and biofilm of a mature tank. Get those two things right — healthy stock and an established, algae-rich aquarium — and the oto is a delightful, hardworking nano catfish.
Tank & water
A group of six suits a 40-litre (10-gallon) tank or larger, but the single most important requirement is a mature, established aquarium. Keep 22–27 °C with a gentle filter and well-oxygenated water — otos dislike low oxygen.
- Algae to graze: add otos only once the tank has run for a few months and grows soft algae and biofilm.
- Planted and gentle: plants and driftwood give grazing surfaces and cover.
- Pristine water: they are sensitive to poor quality — keep up maintenance.
Feeding
Otos are dedicated herbivores. Their staple is the soft algae and biofilm in the tank, supplemented with blanched vegetables — courgette, cucumber and de-shelled peas — and the occasional algae wafer. If your tank is very clean, you must feed vegetables daily. See the fish food hub and our best fish food picks. A sunken belly is a warning sign of an underfed oto.
Tankmates
Peaceful and timid, otos need gentle company — small tetras, rasboras, corydoras, bettas and cherry shrimp, with which they mix beautifully. Avoid anything large, boisterous or aggressive. They pair well with other peaceful algae-eaters like the bristlenose pleco.
Frequently asked questions
The otocinclus is a brilliant little algae-grazer for the patient keeper. Give it healthy stock, a mature algae-rich tank, a group of six and vegetable top-ups, and it will earn its keep for years.
Otocinclus catfish — frequently asked questions
Why do otocinclus need a mature tank?
Because they feed almost entirely on the soft algae and biofilm that only grow in an established aquarium. In a new, spotless tank they slowly starve. Add them only to a tank that has been running for a few months and has visible algae growth.
Are otocinclus hard to keep?
They are sensitive on two fronts: many arrive weak and underfed from the shop, and they can starve in a too-clean tank. Given a mature, algae-rich tank, a group of six or more, and supplementary vegetables, established otos are peaceful and rewarding.
How many otocinclus should I keep together?
At least six. Otos are shoaling fish that graze together and feel secure in numbers, becoming much more active and confident in a group. Lone otos tend to hide and fade.
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