Encyclopaedia

FishFreshwaterExpert

Otocinclus (Oto Macrospilus)

Otocinclus macrospilus

Aesthetically almost identical to O. vittatus, it is the classic and tireless 'Otocinclus' of the aquarium market. It is distinguished by the large diamond spot on the tail that DOES NOT merge cleanly with the lateral body line.

Taxonomy

Class:Actinopteri

Order:Siluriformes

Family:Loricariidae

Subfamily:Hypoptopomatinae

Genus:Otocinclus

Species:Otocinclus macrospilus

Check out Otocinclus (Oto Macrospilus) on Atlarium

PracticeRecognition quizzesPhotos, names, origins, and puzzles to review Atlas species.Open quizzes

Water Temperature

21 - 26 °C

pH Value

5.5 - 7.5

Water type

Freshwater

Tank level

Bottom and middle

Adult size

4 cm

Minimum tank volume

>= 30 L

Minimum group

>= 1

1 - 12 dGH

1 - 6 dKH

TDS

25 - 240 ppm

Conductivity

39 - 375 uS/cm

Species description

Geographical Origin and Habitat: Fascinating nano-loricariid endemic to the immense and lush basin of the Ucayali, Marañón, and Napo rivers (Peru, Ecuador, and Colombia). Assembles in myriads, forming swarms of thousands of trembling and ravenous individuals in slow streams (igarapés) surrounded by the opulent Amazonian canopy, sticking firmly to the flooded edges covered with grass and tangled roots.

Taxonomy and Morphology: Loricariidae family. O. macrospilus is without a doubt the most commonly imported species along with vittatus, although almost everywhere passed off with the old name of 'O. affinis'. Extremely delicate bone structure, microscopic size like a darting dart (4 cm / 1.6 inches maximum, even less for males). Armed with the typical and highly evolved removing labial suction cup. Physically defenseless against attacks (it defends itself only by fleeing in a flash in a group and hiding).

Social Behavior: Physiologically in need of gregarious contact (Thigmotaxis). Animal with a highly delicate psyche and a habitual prey in nature; ISOLATION WILL KILL IT psychologically. It is mandatory to insert them in minimum schools of 6-10 specimens upwards. Reassured by its peers, the school becomes the surface scavenger par excellence: in perfect synchrony they float from the glass to the expanded leaves, meticulously sifting and dusting the fragile foliage of green debris without scratching it. Absolute phobia of jerky absolute darkness, prefers to sleep in dense suspended forests visually sheltered.

Coloration and Sexual Dimorphism: The masterpiece of Amazonian camouflage ('cryptic coloration'). Ochre or cement gray background dotted with faded speckles on the back, simulating the bright light falling on pebbles. Abdomen of a blinding immaculate and very smooth pearl titanium white. HOW TO DISTINGUISH IT FROM OTHER OTOCINCLUS? It is the only one to have, at the base root of the tail, a massive defined black spot (like a large diamond exclamation mark) WHICH IS SEPARATED and does not merge in continuous horizontal unbroken continuity with the very long and straight broken blackish line ('vitta') of the back. Here too, females visibly dilated by the spherical and abdominal swelling of stable clutches, and puny males like smooth and bony and compressed mini torpedoes.

Care, breeding and tankmates

Aquarium Setup: THE ABSOLUTE LETHAL MISTAKE is its early adoption in a clean, brand new aquarium. An O. macrospilus placed in a tank without microscopic cobwebs of mature brown algal colonies ('Bio-film and Aufwuchs'), is condemned to empty internally, languishing atrociously frightened until the vital mortal asphyxiating end. Demands the old and inexorable mature green filmy organic safety, dense marsh vegetation in the aquarium where to perch and limpid filtered sweet water.

Diet and Feeding: Pure vegan in nature, absolute desperate aseptic in extremis. DOES NOT eat corpses or dirt and feces. Incessantly demolishes soft and asphyxiating dusty green algae (green dust) and mucous silicon brown diatom algae on shaded glass. (Without the necessary help of hard Spirulina specially round pressed in a very green base, it will go to a catabolic collapse from exhausted plant aquarium hunger anorexia if it has polished it properly; Biweekly integrate without excuses rounds of boiled pumpkin, thick boiled raw zucchini slice, soaked spinach skins as succulent baby food that they will devour in joyful groups hanging vertically on the glass endlessly).

Water Quality: Manageable difficulty but without serious chemical errors on the part of the ignorant incautious novice (it is the 'canary in the coal mine', the first to die of pollution). Suffers at the level of neurological collapse the asphyxiating devastating peak of fatal lethal ammonia of unresolved tanks in biological newborn unripe unstable cycle and brutal fast cold winter temperature swings of careless sudden changes without urban heater or sudden freezing bucket water changes. Being thermophilic but of rain shadow it is a comfortable lover of the stainless 21 - 26°C (70-79°F) maximums, if cooked in summer without oxygen or with hot thermophilic tropical Amazonian Discus fish at asphyxiating 30 degrees (86 F) it will perish suffocated. Demands neutral/acidic Amazonian weakly soft water tolerating safe urban medium tolerances ph 5.5 to moderate 7.5 weak urban GH without lethal poisonous limestone.

Compatibility and Cohabitation: Helpless ethereal ghost companion and ignored foolish and minuscule in degree of escape asphyxiated by helpless cowardly fright. Obligation to pair it with very tiny passive static asocial miniature harmless very slow equal or more cowardly foolish and blind peaceful flocks: inestimable safe and docile friend with highly delicate minuscule livebearer fry without hitting them and microscopic helpless snails and peaceful transparent nice colored neocaridina and red cherry shrimp cohabiting common zucchini adorable and rasbora fish and corydoras. Absolute ban and mortal homicidal madness to insert it as a tragic dinner with heavy slow South American Cichlids huge Oscars (would swallow it but the brave defensive minuscule desperate Oto would open its tremendous cross-shaped agony weapon extruded and would tragically die strangling the devourer choking him mortal drowned tragic fatal double killer); phobic stressful lethal phobias if you harass it with heavy Clown Loaches or fast giant red-tailed shark labeo fish scary harassing mortal fast aggressors.

Aquarium Breeding: Prodigious species reproducible but unexpected rare amateur complex magical invisible luck. If satiated happy round obese with juicy green algae organic spirulina vegetables and in pure immaculate stable mature wild Amazonian Dutch thickets in phobias of cold rainwater dissolved as a waterfall the thick breeders will excite furious acrobatic spermatic caroms hiding slender impalpable minuscule microscopic diaphanous spheres scattered scattered and untied from piles abandoning them under umbrella echinodorus leaves and hatched fast without defenses in invisible helpless transparent static pale exposed fry worms that if they do not have in that mature rich tub a sticky mossy infused putrefied tasty invisible algal bio-film where the tiny mouth blindly rubs asphyxiating they will die lethal evaporated by micro starvations vanished malnourished in devastating hunger swallowed massacred losing them all.

Risks and Diseases: Lethal Rotten Intestinal Occlusion due to lack of biofilm and asphyxiating starvation of prolonged vegetarian algae or languid inauspicious malnourished static death and pale sad gastric suffocation by slit belly tragically put aseptic in sterile glass newly scrubbed bought pristine cruel by ignorant stressful embittered amateurs emptied without tablets and asphyxiated by drowning in solitude lethargy fright stress static moribund in group less than three devastated cowards, and pure allergic devastatingly fulminating toxic poisons without forgiveness to the cursed useless snail killer copper killer or bestial hyper chemical excess fertilized of commercial Dutch that burns them in dead hours.

Geographic Origin and Distribution

Fascinating nano-loricariid endemic to the immense and lush basin of the Ucayali, Marañón, and Napo rivers (Peru, Ecuador, and Colombia). Assembles in myriads, forming swarms of thousands of trembling and ravenous individuals in slow streams (igarapés) surrounded by the opulent Amazonian canopy, sticking firmly to the flooded edges covered with grass and tangled roots.

Origin

Amazon, Orinoco, and GuianasEast Asia

Fish profile

Temperament: Semi-aggressive
Diet: Omnivore
Sex ratio: School
Feeding frequency: Twice daily
Bioload: They have an incredibly low bioload due to their miniature size. Their waste production is easily handled by biological filtration. They are perfect for heavily planted, low-waste setups.
Flow: Stagnant
Reproduction: Oviparous
Compatibility & tankmates: They are incredibly docile and make perfect community fish. They must be housed with similarly small and peaceful tank mates. Keeping them with aggressive species will lead to extreme stress.
Tank level: Middle/Bottom

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Phylogenetic uniqueness (PD50): 0.5
Bayesian Length-Weight: a = 0.00977, b = 3.06

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

Recommendations grouped by close relatives, companion choices, and similar care.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Otocinclus (Oto Vittatus)

Otocinclus vittatus

Species description

Care, breeding and tankmates

Geographic Origin and Distribution

Origin

Fish profile

Scientific Parameters & Models

Image gallery

Related species

Variants and close relatives

Otocinclus (Oto Vittatus)

Hoppe's otocinclus

Zebra otocinclus

Otocinclus (Dwarf Sucker)

Pitbull pleco

Twig Catfish

Snowball Pleco

Giant-eye Otocinclus

Mato Grosso Ancistrus

Queen Arabesque Pleco (L260)

Super White Pleco (L236)

Orinoco Twig Catfish

Monte Dourado Pleco (L411)

Ocelot Pleco (L174)

Albino Bristlenose Pleco

Green Phantom Pleco

Recommended companions

Bucephalandra pygmaea "Bukit Kelam / Sintang"

Bucephalandra pygmaea "Kapit"

Bucephalandra sordidula

Bucephalandra sp. "Bodok"

Bucephalandra sp. "Braun-rot narrow"

Bucephalandra sp. "Braun-rot" ("Serimbu")

Bucephalandra sp. "Gunung Sumpit"

Bucephalandra sp. "Kedagang"

Blyxa alternifolia

Blyxa cf. vietii

Ammannia latifolia

Ammannia sp. 'Bonsai'

Amblystegiaceae sp. "Manaus"

Bacopa sp. "Japan"

Bolbitis heteroclita

Barbula sp.

Similar care

Agulha Tetra

False Spotted Corydoras

Blue Panaque (L239)

Cryptic Corydoras

Tapajós Royal Pleco (L027)

False Bandit Cory

Agassiz's Corydoras

Blacktop Corydoras

Concolor Cory

Reticulated Corydoras

Blackmask Corydoras

Hi-Fin Green Phantom Pleco (L200)

Keyhole cichlid

Bolivian Ram

Copeland's Tetra

Guahibo Pleco