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.
Golden Oto At a Glance
Golden Oto Tank Requirements
Will Golden Oto fit in your tank?
Care guides tell you what Golden Oto needs, the next question is whether your tank can safely provide it. Test Golden Oto against your tank size, maintenance needs, and the fish you already keep before you buy.
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Golden Oto Water Parameters
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Golden Oto Temperament & Compatibility
Golden Oto Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard
The standard form available in the aquarium trade. Due to their small size and social nature, keeping a group of 6 or more is critical for their confidence and survival, ensuring they actively graze in the open.
Same care requirements as the base species
Also known as: Wild Type
Golden Oto Care Guide Summary
The Golden Oto, scientifically known as Macrotocinclus affinis, belongs to the Catfish family group. Adults reach a maximum size of approximately 4.5 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 Golden Oto 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 27°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 Golden Oto is best suited for fishkeepers who can provide a carefully planned setup. The Golden Oto is typically available in one standard form.
Golden Oto Habitat Setup
When setting up an aquarium for the Golden Oto, 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, 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.
Golden Oto Compatibility Notes
Classified as peaceful, the Golden Oto 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.
Golden Oto Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Golden Oto.
10 Gallon Standard
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
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Frequently Asked Questions About Golden Oto
How big does Golden Oto get?
Golden Oto (Macrotocinclus affinis) typically reaches a maximum adult size of approximately 4.5 cm. They have a depressed body shape and a slow growth rate.
What tank size does Golden Oto need?
A minimum aquarium volume of 38 litres and a tank length of at least 45 cm are recommended for Golden Oto. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Golden Oto need?
Golden Oto thrives in freshwater only conditions with a temperature range of 21–27°C, a pH between 6 and 7.5, and a general hardness of 4–15 dGH. A moderate water flow is preferred.
Is Golden Oto peaceful or aggressive?
Golden Oto is classified as peaceful with an aggression score of 0 out of 10. They are generally well-suited to peaceful community tanks.
How many Golden Oto should be kept together?
Golden Oto 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 Golden Oto have any special tank requirements?
Yes. Golden Oto benefits from established algae (otocinclus), plants - densely covered, and smooth gravel (sensitive barbels) in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Top Tank Mates for Golden Oto
These fish are strong compatibility matches for Golden Oto based on water preferences, temperament, adult size, and tank behavior.
Marbled Hatchetfish
Carnegiella strigata
Ideal Tank MatesClown Killifish
Epiplatys annulatus
Ideal Tank MatesPurple Zebra Shrimp
Potamalpheops sp.
Ideal Tank MatesGreen Neon Tetra
Paracheirodon simulans
Ideal Tank MatesGarnet Tetra
Hemigrammus pulcher
Ideal Tank MatesMarbled Whiptail
Loricaria simillima
Ideal Tank MatesPlants That Suit Golden Oto
These plants pair well with Golden Oto 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 Golden Oto
Otocinclus
Otocinclus vittatus
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.
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.
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.
Sparkling Gourami
Trichopsis pumila
A stunning nano species known for its iridescent blue/green eyes, body spots, and ability to make audible 'croaking' sounds. Unlike many anabantoids, they are social and best kept in groups. However, they are efficient micropredators that will hunt shrimp fry and pests like hydra. Requires stable water parameters and dense planting.
Dwarf Petricola
Synodontis lucipinnis
A highly active, peaceful, and gregarious catfish endemic to Lake Tanganyika. Often confused with Synodontis petricola, S. lucipinnis stays smaller. They require hard, alkaline water (Rift Lake parameters) and must be kept in groups to feel secure. Unlike many bottom-dwelling catfish, they spend a significant amount of time actively swimming in the middle water column during the day.
Brown Hoplo Catfish
Hoplosternum littorale
A heavily armored, highly adaptable catfish native to South America. It possesses the unique ability to breathe atmospheric air using a modified intestine, allowing it to survive in oxygen-depleted swamps. They are peaceful but boisterous bottom-dwellers with voracious appetites. They constantly forage, which can result in the uprooting of delicate plants.