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Otocinclus
Otocinclus affinis
Also known as: oto, dwarf suckermouth, Oto, Dwarf suckermouth
Fishori provides conservative planning guidance, not guarantees.
Based on multiple reputable aquarium care sources with strong agreement. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
The true peaceful algae-eater. Extremely sensitive to new tanks and ammonia spikes. A high-mortality fish when added too early.
Best for
Mature, well-cycled planted tanks 60L+ with a constant algae and biofilm supply.
Avoid if
Your tank is under 6 months old, you have aggressive cichlids, or you can't supply blanched veggies during algae droughts.
Top things that go wrong
- Shrimp & snails. Shrimp: compatible in most setups. Cherry shrimp and other dwarf species coexist with peaceful small fish, though baby shrimp are food for almost any fish that gets to them.
Common mistakeAdding otocinclus in the first two months. No established biofilm means starvation. They need a mature tank with visible algae already present.
What most shops don't tell you
- 1.A trio in a brand new tank with no biofilm. A hungry oto is dead inside a fortnight.
- 2.Housing otos in hot brash cichlid tanks without a soft algae or vegetable plan.
- 3.A group of four or more, all from the same shop tank. Otos crash in a young setup or after a long transit without food. Drop in algae wafers or a blanched courgette ring during slow weeks.
About this species
Otocinclus are 4 to 5 cm catfish that graze algae and biofilm in mature planted tanks. Imports arrive thin from the shop and need biofilm waiting for them.
- Bristlenose Pleco80L min · same fish family
- Siamese Algae Eater100L min · same fish family
- Clown Pleco110L min · same fish family
- Royal pleco500L min · same fish family
- Common Pleco600L min · same fish family
- Adolfoi coryalso intermediate peaceful, similar tank size
- Bamboo Shrimpalso intermediate peaceful, similar tank size
- Black ruby barbalso intermediate peaceful, similar tank size
- Brown / hockey-stick pencilfishalso intermediate peaceful, similar tank size
- Cardinal Tetraalso intermediate peaceful, similar tank size
- Celebes Rainbowfishalso intermediate peaceful, similar tank size
- Amano Shrimp tank mateslists this fish as a safe and recommended mate
- Apistogramma Borellii tank mateslists this fish as a safe and recommended mate
- Apistogramma Macmasteri tank mateslists this fish as a safe and recommended mate
- Bamboo Shrimp tank mateslists this fish as a safe and recommended mate
- Beckford Pencilfish tank mateslists this fish as a safe and recommended mate
- Betta tank mateslists this fish as a safe and recommended mate
- Blue Dream Shrimp tank mateslists this fish as a safe and recommended mate
- Celebes Rainbowfish tank mateslists this fish as a safe and recommended mate
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease41
- Peacefulness90
- Community fit86
- Small-tank fit100
- Hardiness57
- Energy24
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Rough 90L+ layout: one calm centrepiece, 8–12 small tetras/rasboras, 6–8 corydoras-type bottom fish — verify every name in the pair checker before buying.
Safe directions on file include: Neon Tetra, Corydoras Catfish, Cherry Barb.
Tank mate intelligence
Pairs with neon tetras, harlequin rasboras, corydoras, dwarf gouramis, and shrimp. Skip aggressive cichlids and fast top-water predators.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Otocinclus + Neon Tetra
- Try Neon Tetra — open the pair check.
- Try Corydoras Catfish — open the pair check.
- Try Cherry Barb — open the pair check.
- Try Betta — open the pair check.
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Strictly peaceful and shoaling. Skittish in bright open tanks. They want plants, wood, and shaded spots.
Stress / aggression triggers on file
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Not a predator toward similarly-sized community fish. The usual community caveats about mouth size still apply for very small fry or shrimp.
Territory: Not strongly territorial, but still claims a working area in the tank. Give it room to settle without overlapping the next species' patch.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Often calm on the glass — bursts of movement around food or tank disturbance.
- Shoaling/schooling: most colour and confidence show when the group meets **4+**.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Low listed risk — still watch new introductions.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
soft
Diet
herbivore
Vegetable matter, algae, and plant-based prepared foods. Long-term protein-only feeding causes bloat in herbivorous species.
Shrimp & snails
Shrimp: compatible in most setups. Cherry shrimp and other dwarf species coexist with peaceful small fish, though baby shrimp are food for almost any fish that gets to them.
Shoaling species. Buy 4 or more of one species together. Smaller schools sulk, lose colour, and redirect their schooling energy at whatever else is in the tank.
Egg scatterers and schoolers still spawn in stable tanks. Have a plan for the fry, or accept that the parents and tank mates will eat them in a community setup.
- Hold 20 to 27 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 6 to 7.5 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Schooling species. Buy 4 or more from the same tank on the same day before adding any centrepiece fish.
- Tank volume meets or exceeds 60L published minimum for adults.
- You can stock at least 4 individuals (group welfare).
- Heater can hold 20–27°C without cooking cooler-water tank mates.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 60L minimum tank needs a filter rated for at least 240L/hr turnover and a heater to hold 20–27°C reliably.
Plant suggestions
Otocinclus does well in planted tanks. Plants compatible with 20–27°C and pH 6–7.5:
Profile status: verified · Evidence tier: high · 5 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Otocinclus macrospilus (Otocinclus ‘affinis’ / trade oto stand-in)
Primary stand-in: SF profile for O. macrospilus. Shop 'O. affinis'/'otocinclus' labels are often misidentified. Verify the fish against a good key, not a single import sticker.
- FishBase. Otocinclus affinis
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Otocinclus affinis
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
- FishBase. Otocinclus vittatus
Taxonomy, distribution, and typical max length in natural/wild contexts (cross-check to aquarium import lines).
- Wikipedia. Otocinclus
Encyclopaedia overview; use specialist aquarium sources for your stock's real temperature/pH/footprint needs.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.