Otocinclus Arnoldi (Otocinclus arnoldi)

Description

Otocinclus Arnoldi (Otocinclus arnoldi)

Tiny, peaceful and incredibly hardworking, Otocinclus arnoldi is one of the finest algae-grazing catfish available for planted aquariums. Its gentle nature, compact size and constant grazing behaviour make it an excellent companion for nano aquariums and peaceful community tanks with stable, mature water conditions.

Quick Facts

  • Scientific name: Otocinclus arnoldi
  • Common name: Otocinclus Arnoldi, Arnold's Otocinclus
  • Current size: Approximately 2–3 cm
  • Adult size: Approximately 4–5 cm
  • Tank size: 40L+ recommended
  • Difficulty: 🟡 Moderate
  • Temperament: Extremely peaceful
  • Minimum group: 6+ recommended

Is this for you?

✔️ Perfect if:

  • You have a mature planted aquarium with natural algae and biofilm.
  • You want one of the safest algae-grazing fish for nano aquariums.
  • You enjoy peaceful schooling fish with fascinating natural behaviour.
  • You can keep them in a proper group of six or more.

❌ Avoid if:

  • Your aquarium is newly established or still cycling.
  • You plan to keep only one or two individuals.
  • You keep aggressive or boisterous fish.
  • You expect them to survive solely by cleaning the aquarium.

Why choose Otocinclus arnoldi?

Otocinclus arnoldi is one of the smallest catfish available in the aquarium hobby, yet it performs an important role by constantly grazing soft algae, biofilm and microorganisms from plant leaves, driftwood and aquarium glass. Their peaceful nature makes them an excellent addition to aquascapes where larger algae eaters would simply be too big.

Unlike larger plecos, Otocinclus remain tiny throughout their lives and rarely disturb plants or décor. They spend much of the day moving together in loose groups, methodically cleaning surfaces while adding subtle movement to the aquarium.

Although hardy once established, they should only be introduced into mature aquariums where natural grazing opportunities already exist. Stable water quality and regular supplementary feeding are the keys to long-term success.

Benefits

  • Excellent grazer of soft algae and biofilm
  • Perfect for planted and nano aquariums
  • Tiny adult size
  • Completely peaceful community fish
  • Safe with freshwater shrimp and delicate plants
  • Interesting schooling and grazing behaviour

Care made simple

  • Temperature: 22–27°C
  • pH: 6.0–7.5
  • Diet: Natural biofilm, soft algae, algae wafers, spirulina foods, blanched zucchini, cucumber and spinach
  • Water: Very clean, stable and well oxygenated with low nitrate levels
  • Substrate: Sand or fine gravel
  • Setup: Dense plants, driftwood, smooth stones and established algae-covered surfaces
  • Keep in groups of at least six to encourage natural behaviour and reduce stress.
  • Supplement their diet once natural algae becomes limited.

Pairs perfectly with

  • Cardinal Tetras
  • Ember Tetras
  • Pygmy Corydoras
  • Honey Gouramis
  • Cherry Shrimp and other Neocaridina shrimp
NTA Insight:
Otocinclus are often purchased purely as algae eaters, but the healthiest fish are those introduced into mature aquariums with abundant natural biofilm already available. At NTA, we recommend adding them only after an aquarium has been running successfully for several months. Once established, they become one of the most useful and enjoyable nano catfish available.

FAQ

Are Otocinclus good algae eaters?

Yes. They are among the best fish for controlling soft algae and biofilm in planted aquariums, although they will not remove tougher algae such as Black Beard Algae or mature hair algae.

Should they be kept alone?

No. Otocinclus are naturally social fish and should always be kept in groups of at least six, with larger groups providing even greater confidence and more natural behaviour.

Can they live with shrimp?

Absolutely. Their peaceful nature makes them one of the safest catfish to keep alongside Neocaridina and Caridina shrimp.

Do they eat plants?

No. Healthy Otocinclus graze on algae and biofilm growing on plant leaves without damaging the plants themselves.

Why do Otocinclus sometimes struggle in new aquariums?

New aquariums often lack the natural biofilm and microorganisms they depend on. Introducing them into mature, established systems greatly improves their long-term survival.

Are they suitable for beginners?

They can be, provided the aquarium is fully cycled, mature and stable. They are less forgiving of poor water quality than many other small community fish.

How long does Otocinclus arnoldi live?

With excellent water quality, proper nutrition and a stress-free environment, they commonly live between 3 and 5 years.

Otocinclus Arnoldi (Otocinclus arnoldi)

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SKU: OTOS

19 in stock  

$18.00


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    Description

    Otocinclus Arnoldi (Otocinclus arnoldi)

    Tiny, peaceful and incredibly hardworking, Otocinclus arnoldi is one of the finest algae-grazing catfish available for planted aquariums. Its gentle nature, compact size and constant grazing behaviour make it an excellent companion for nano aquariums and peaceful community tanks with stable, mature water conditions.

    Quick Facts

    • Scientific name: Otocinclus arnoldi
    • Common name: Otocinclus Arnoldi, Arnold's Otocinclus
    • Current size: Approximately 2–3 cm
    • Adult size: Approximately 4–5 cm
    • Tank size: 40L+ recommended
    • Difficulty: 🟡 Moderate
    • Temperament: Extremely peaceful
    • Minimum group: 6+ recommended

    Is this for you?

    ✔️ Perfect if:

    • You have a mature planted aquarium with natural algae and biofilm.
    • You want one of the safest algae-grazing fish for nano aquariums.
    • You enjoy peaceful schooling fish with fascinating natural behaviour.
    • You can keep them in a proper group of six or more.

    ❌ Avoid if:

    • Your aquarium is newly established or still cycling.
    • You plan to keep only one or two individuals.
    • You keep aggressive or boisterous fish.
    • You expect them to survive solely by cleaning the aquarium.

    Why choose Otocinclus arnoldi?

    Otocinclus arnoldi is one of the smallest catfish available in the aquarium hobby, yet it performs an important role by constantly grazing soft algae, biofilm and microorganisms from plant leaves, driftwood and aquarium glass. Their peaceful nature makes them an excellent addition to aquascapes where larger algae eaters would simply be too big.

    Unlike larger plecos, Otocinclus remain tiny throughout their lives and rarely disturb plants or décor. They spend much of the day moving together in loose groups, methodically cleaning surfaces while adding subtle movement to the aquarium.

    Although hardy once established, they should only be introduced into mature aquariums where natural grazing opportunities already exist. Stable water quality and regular supplementary feeding are the keys to long-term success.

    Benefits

    • Excellent grazer of soft algae and biofilm
    • Perfect for planted and nano aquariums
    • Tiny adult size
    • Completely peaceful community fish
    • Safe with freshwater shrimp and delicate plants
    • Interesting schooling and grazing behaviour

    Care made simple

    • Temperature: 22–27°C
    • pH: 6.0–7.5
    • Diet: Natural biofilm, soft algae, algae wafers, spirulina foods, blanched zucchini, cucumber and spinach
    • Water: Very clean, stable and well oxygenated with low nitrate levels
    • Substrate: Sand or fine gravel
    • Setup: Dense plants, driftwood, smooth stones and established algae-covered surfaces
    • Keep in groups of at least six to encourage natural behaviour and reduce stress.
    • Supplement their diet once natural algae becomes limited.

    Pairs perfectly with

    • Cardinal Tetras
    • Ember Tetras
    • Pygmy Corydoras
    • Honey Gouramis
    • Cherry Shrimp and other Neocaridina shrimp
    NTA Insight:
    Otocinclus are often purchased purely as algae eaters, but the healthiest fish are those introduced into mature aquariums with abundant natural biofilm already available. At NTA, we recommend adding them only after an aquarium has been running successfully for several months. Once established, they become one of the most useful and enjoyable nano catfish available.

    FAQ

    Are Otocinclus good algae eaters?

    Yes. They are among the best fish for controlling soft algae and biofilm in planted aquariums, although they will not remove tougher algae such as Black Beard Algae or mature hair algae.

    Should they be kept alone?

    No. Otocinclus are naturally social fish and should always be kept in groups of at least six, with larger groups providing even greater confidence and more natural behaviour.

    Can they live with shrimp?

    Absolutely. Their peaceful nature makes them one of the safest catfish to keep alongside Neocaridina and Caridina shrimp.

    Do they eat plants?

    No. Healthy Otocinclus graze on algae and biofilm growing on plant leaves without damaging the plants themselves.

    Why do Otocinclus sometimes struggle in new aquariums?

    New aquariums often lack the natural biofilm and microorganisms they depend on. Introducing them into mature, established systems greatly improves their long-term survival.

    Are they suitable for beginners?

    They can be, provided the aquarium is fully cycled, mature and stable. They are less forgiving of poor water quality than many other small community fish.

    How long does Otocinclus arnoldi live?

    With excellent water quality, proper nutrition and a stress-free environment, they commonly live between 3 and 5 years.

    Live Arrival & Ordering FAQ

    Why do livestock prices sometimes change?

    Unlike manufactured products, fish and shrimp continue to grow and develop over time. Their value changes as they increase in size, develop colour, or become breeding pairs.

    Our prices are based on the current size, quality and availability of each specimen. While pricing often remains stable for around 3–4 months, it may be updated at any time to reflect these changes.

    We always aim to offer healthy, high-quality livestock at fair and competitive prices.

    Do you offer a live arrival guarantee?

    Yes. All livestock is covered by our Live Arrival Guarantee.

    In the rare event of DOA, please contact us promptly with clear photos of the livestock in the original unopened bag.

    Please review our full DOA and store policies before purchase.

    Can you ship to all states in Australia?

    No. Due to state restrictions, we cannot ship livestock or live plants to WA and TAS.

    What should I check before ordering?

    Before placing an order, make sure:

    • Your tank is fully cycled and stable
    • Your aquarium has enough space for the species
    • Your current livestock are compatible in temperament, size, and requirements
    • Your water parameters, habitat, and temperature suit the species
    • You are not adding too many fish at once
    What should I expect when my fish arrives?

    It is normal for fish, shrimp, or snails to look pale, stressed, or less active after shipping.

    This is temporary. Most livestock will settle and regain colour within a few days.

    How long does it take for fish to settle in?

    Most livestock will take 3–7 days to fully adjust to their new environment.

    Should I feed my fish immediately after arrival?

    No. We recommend waiting 24 hours before feeding to allow them to settle.

    If you already have fish in your tank, feeding them before introducing new arrivals can help reduce stress.

    Why do fish sometimes struggle after being added to a tank?

    In most cases, issues are caused by tank conditions, not shipping.

    • Uncycled or unstable tanks
    • Poor water parameters
    • Overstocking
    • Unsuitable tank mates
    What is Nano Tanks Australia’s main tip for new livestock?

    Most livestock losses happen in immature or unstable tanks, not during shipping.

    If your setup is not fully established, the risk to new arrivals is significantly higher.

    Not sure if this fish is right for your setup?

    If you are unsure whether this species suits your setup, contact us before ordering and we’ll help point you in the right direction.

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