A small, peaceful, and highly popular algae-eating catfish native to South America. They are obligate shoaling fish that thrive in mature, heavily planted aquariums with steady water parameters and a constant supply of soft green algae and biofilm. They are extremely sensitive to uncycled or pristine/new tanks without natural food sources.
Otocinclus At a Glance
Otocinclus Tank Requirements
Will Otocinclus fit in your tank?
Care guides tell you what Otocinclus needs, the next question is whether your tank can safely provide it. Test Otocinclus against your tank size, maintenance needs, and the fish you already keep before you buy.
Otocinclus Water Parameters
Otocinclus Temperament & Compatibility
Otocinclus Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard
The standard Otocinclus available in the trade. Must be kept in groups of at least 6 to feel secure. Ensure the tank is fully mature (running for several months) before adding them to guarantee sufficient biofilm and algae growth.
Same care requirements as the base species
Also known as: Wild Type Oto, Common Oto
Otocinclus Care Guide Summary
The Otocinclus, scientifically known as Otocinclus vittatus, belongs to the Catfish family group. Adults reach a maximum size of approximately 4 cm and have a depressed body shape with a slow growth rate. Classified as peaceful, this species primarily occupies the mid-level and bottom zones of the aquarium and produces a low level of biological waste.
To thrive, the Otocinclus requires a freshwater only aquarium with a minimum volume of 38 litres and a tank length of at least 45 cm. Water temperature should be maintained between 21°C and 26°C, with a pH range of 6–7.5 and a general hardness of 4–15 dGH. A moderate water flow is preferred.
Due to its specialist needs, the Otocinclus is best suited for fishkeepers who can provide a carefully planned setup. The Otocinclus is typically available in one standard form.
Otocinclus Habitat Setup
When setting up an aquarium for the Otocinclus, a moderate water flow best suits their natural preferences. Because this species occupies the mid-level and bottom zones, the aquarium layout should prioritise open swimming space in the centre of the tank for free movement and sufficient floor space with hiding spots among rocks, wood, or dense planting. Useful additions include smooth gravel or rounded substrate to protect their sensitive barbels, driftwood, which can serve as both a hiding place and a dietary supplement, an established tank with natural algae growth, as they depend on it as a primary food source, and dense planting to provide cover, break sightlines, and reduce stress.
Otocinclus Compatibility Notes
Classified as peaceful, the Otocinclus is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, boisterous or fast-moving tankmates may cause this species undue stress. Selecting tankmates that favour different water layers from the mid-level and bottom zones can help reduce competition and territorial overlap.
Who Otocinclus Is Actually For
Otocinclus is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 6. It makes the most sense for a hobbyist who will actually build around its needs, especially established algae.
The most common mistake is buying Otocinclus for looks first and only later discovering how its adult size, behavior, or bioload changes the whole tank plan. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.
Otocinclus Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Otocinclus.
10 Gallon Standard
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
Show 22 more tank sizes
Frequently Asked Questions About Otocinclus
How big does Otocinclus get?
Otocinclus (Otocinclus vittatus) typically reaches a maximum adult size of approximately 4 cm. They have a depressed body shape and a slow growth rate.
What tank size does Otocinclus need?
A minimum aquarium volume of 38 litres and a tank length of at least 45 cm are recommended for Otocinclus. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Otocinclus need?
Otocinclus thrives in freshwater only conditions with a temperature range of 21–26°C, a pH between 6 and 7.5, and a general hardness of 4–15 dGH. A moderate water flow is preferred.
Is Otocinclus peaceful or aggressive?
Otocinclus is classified as peaceful with an aggression score of 0 out of 10. They are generally well-suited to peaceful community tanks.
How many Otocinclus should be kept together?
Otocinclus is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Otocinclus have any special tank requirements?
Yes. Otocinclus benefits from established algae (otocinclus), plants - densely covered, smooth gravel (sensitive barbels), and driftwood (digestion/hiding) in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Useful setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- April 28, 2026
- Last updated
- April 28, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for Otocinclus
These fish are strong compatibility matches for Otocinclus based on water preferences, temperament, adult size, and tank behavior.
Marbled Hatchetfish
Carnegiella strigata
Ideal Tank MatesClown Killifish
Epiplatys annulatus
Ideal Tank MatesSpotted Hillstream Loach
Gastromyzon punctulatus
Ideal Tank MatesTrapdoor Snail
Cipangopaludina chinensis
Ideal Tank MatesParallel Cory
Corydoras parallelus
Ideal Tank MatesPurple Zebra Shrimp
Potamalpheops sp.
Ideal Tank MatesPlants That Suit Otocinclus
These plants pair well with Otocinclus based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Afzel's Anubias
Anubias afzelii
Amazon Sword
Echinodorus amazonicus
Anacharis
Egeria densa
Anubias Barteri
Anubias barteri
Baby Tears
Lindernia rotundifolia
Balansae
Cryptocoryne crispatula
Fish Similar to Otocinclus
Vestitus Otocinclus
Otocinclus vestitus
Otocinclus are among the smallest and most peaceful algae-eating catfish in the aquarium hobby. They are strictly herbivorous, constantly grazing on soft green algae and biofilm on plants and glass. They are highly social and must be kept in groups. Crucially, Otocinclus are notoriously sensitive to newly setup aquariums and require mature, stable water conditions with plenty of surfaces to graze on.
Zebra Oto
Otocinclus cocama
A strikingly patterned, highly sought-after nano suckermouth catfish native to Peru. Like other Otocinclus, they are completely peaceful and excellent algae eaters. However, they are notably sensitive to water parameters and require a well-established, mature aquarium with plenty of biofilm, soft algae, and driftwood to thrive. They must be kept in groups to feel secure.
Golden Oto
Macrotocinclus affinis
A highly popular nano suckermouth catfish, prized in planted tanks for their voracious appetite for diatoms and soft brown algae. They are incredibly peaceful but notoriously delicate during acclimatization, requiring well-established, mature aquariums with plenty of biofilm and stable water parameters. They are highly social and must be kept in groups.
Bristlenose Pleco
Ancistrus cf. cirrhosus
A highly popular, hardy, and relatively small suckermouth catfish. Excellent algae eaters that stay much smaller than Common Plecos, making them suitable for standard aquariums. They require dietary wood (driftwood) to aid in digestion and plenty of hiding caves.
Common Pleco
Hypostomus plecostomus
A heavily armored, nocturnal catfish famous for eating algae. However, they grow incredibly large, produce massive amounts of waste, and frequently outgrow standard aquariums. They require driftwood in their diet for digestion. As they age, they may become territorial or develop a taste for the slime coat of slow-moving, flat-bodied tank mates.
Tandanus Catfish
Tandanus tandanus
An Australian native, the Tandanus Catfish (or Eel-tailed Catfish) is an incredibly hardy, highly adaptable bottom-dweller. They possess a stout body that tapers into an eel-like tail. While generally peaceful towards large tank mates, they are highly predatory nocturnal scavengers and will eat any fish that fits in their cavernous mouths. Caution: They have sharp, mildly venomous serrated spines on their dorsal and pectoral fins.