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[ARRIVING 16-FEB-2026] Otocinclus Arnoldi Great for Shrimp Tanks and Algae Control 2-4cm

Description

Otocinclus arnoldi (Arnold’s Oto Catfish)

Gentle algae grazer for established nano tanks

Quick Facts

  • Size: ~3–4 cm
  • Tank size: 20–60L+
  • Difficulty: 🟡 Moderate
  • Temperament: Peaceful
  • Best kept: Groups (4+)
  • Plant safe: Yes

Is this for you?

✔️ Good if:

  • Established tank (3–4+ weeks)
  • Looking for light algae grazing support
  • Peaceful community setup
  • Willing to keep a group

❌ Avoid if:

  • New or unstable tank
  • Expecting a full algae solution
  • Aggressive tank mates
  • Keeping only one

Why this fish?

Otocinclus arnoldi is one of the smallest and most peaceful catfish available, making it ideal for nano aquariums. They stay small, are plant-safe, and gently graze on soft algae and biofilm without disturbing your setup.

Common mistakes

  • Adding to new tanks → high mortality
  • Expecting them to clean all algae
  • Keeping them alone
  • Not enough natural food (biofilm)
  • Keeping with aggressive feeders

Care made simple

  • Temperature: 22–26°C
  • Diet: Biofilm + algae wafers
  • Group size: 4+ recommended
  • Water: Clean and stable
  • Tank: Established setups only

Pair with

  • Algae wafers
  • Driftwood
  • Sponge filter
  • Live plants
NTA Insight:
Most issues with Otocinclus come from unstable tanks and lack of food — not shipping. If your tank is too new or too clean, risk increases significantly.

FAQ

Do Otocinclus eat all algae?

No. They mainly eat soft algae and biofilm.

Can I keep just one?

No. They do best in groups of 4 or more.

Why did my Otos die quickly?

Usually due to new tanks, lack of food, or stress.

Do they need feeding?

Yes. Supplement with algae wafers.

[ARRIVING 16-FEB-2026] Otocinclus Arnoldi Great for Shrimp Tanks and Algae Control 2-4cm

Product form

Otocinclus arnoldi (Arnold’s Oto Catfish) Gentle algae grazer for established nano tanks Quick Facts Size: ~3–4 cm Tank size: 20–60L+... Read more

Free pickup in our shop(s)

SKU: OTOS

5 in stock

$21.00 $18.00


All prices include GST
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    Description

    Otocinclus arnoldi (Arnold’s Oto Catfish)

    Gentle algae grazer for established nano tanks

    Quick Facts

    • Size: ~3–4 cm
    • Tank size: 20–60L+
    • Difficulty: 🟡 Moderate
    • Temperament: Peaceful
    • Best kept: Groups (4+)
    • Plant safe: Yes

    Is this for you?

    ✔️ Good if:

    • Established tank (3–4+ weeks)
    • Looking for light algae grazing support
    • Peaceful community setup
    • Willing to keep a group

    ❌ Avoid if:

    • New or unstable tank
    • Expecting a full algae solution
    • Aggressive tank mates
    • Keeping only one

    Why this fish?

    Otocinclus arnoldi is one of the smallest and most peaceful catfish available, making it ideal for nano aquariums. They stay small, are plant-safe, and gently graze on soft algae and biofilm without disturbing your setup.

    Common mistakes

    • Adding to new tanks → high mortality
    • Expecting them to clean all algae
    • Keeping them alone
    • Not enough natural food (biofilm)
    • Keeping with aggressive feeders

    Care made simple

    • Temperature: 22–26°C
    • Diet: Biofilm + algae wafers
    • Group size: 4+ recommended
    • Water: Clean and stable
    • Tank: Established setups only

    Pair with

    • Algae wafers
    • Driftwood
    • Sponge filter
    • Live plants
    NTA Insight:
    Most issues with Otocinclus come from unstable tanks and lack of food — not shipping. If your tank is too new or too clean, risk increases significantly.

    FAQ

    Do Otocinclus eat all algae?

    No. They mainly eat soft algae and biofilm.

    Can I keep just one?

    No. They do best in groups of 4 or more.

    Why did my Otos die quickly?

    Usually due to new tanks, lack of food, or stress.

    Do they need feeding?

    Yes. Supplement with algae wafers.

    Live Arrival & Ordering FAQ

    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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