Red Dwarf Pencilfish (Nannostomus mortenthaleri)

Available in store

Description

Red Dwarf Pencilfish (Nannostomus mortenthaleri)

Tiny, elegant and intensely coloured, the Red Dwarf Pencilfish is one of the most beautiful nano fish available. Mature males develop brilliant crimson-red colouration contrasted by bold black lateral stripes and a fine golden sheen, creating a spectacular display in planted and blackwater aquariums. Peaceful, refined and highly sought after, Nannostomus mortenthaleri is a true feature species for aquarists who appreciate smaller fish with exceptional detail.

Quick Facts

  • Brand: AI Livestock
  • Product type: Misc Fish
  • Size / Capacity: 4 cm
  • Suitable for: Species-appropriate, established aquariums

Is this for you?

✔️ Perfect if:

  • Your aquarium is fully cycled and stable.
  • Adult size, social needs and compatibility have been checked.
  • You can provide the correct water conditions, diet and habitat.
  • You can receive and acclimate live livestock promptly.

❌ Consider something else if:

  • The aquarium is new, uncycled or unstable.
  • Compatibility or long-term space has not been confirmed.
  • You cannot meet the species-specific husbandry requirements.

Why choose Red Dwarf Pencilfish (Nannostomus mortenthaleri)?

It provides a clearly identified livestock option that can be assessed against your aquarium.

Matching adult size, behaviour and water needs helps prevent avoidable stress.

A planned addition is easier to acclimate, feed and monitor.

It is preferable to a similar-looking species when its long-term needs better suit your setup.

Key Benefits

  • Planned selection – Supports matching livestock to a suitable aquarium.
  • Aquarium suitability – Can become a rewarding part of a properly planned community.
  • Clear checks – Encourages confirmation of size, water and compatibility.
  • Long-term care – Keeps husbandry ahead of impulse selection.
  • Specialist support – NTA can help clarify suitability before ordering.

Specifications

  • Capacity / Size: 4 cm
  • Shopify category: Live Animals

Specifications may vary by model or manufacturer revision. Please check the selected variant where applicable.

What's included?

  • The selected live livestock variant.
  • Protective packing appropriate to the available fulfilment method.
  • Care or acclimation guidance where supplied.
  • Only items explicitly stated in the listing are included.

Setup & Use

  1. Prepare and test the aquarium before arrival.
  2. Inspect the package and follow current NTA acclimation guidance.
  3. Introduce the livestock calmly with reduced lighting where appropriate.
  4. Observe behaviour and compatibility closely.
  5. Maintain stable water and feed an appropriate diet.

Maintenance

Regular inspection and appropriate care help keep this product or livestock in suitable condition.

  • Test water regularly.
  • Maintain stable, species-appropriate parameters.
  • Feed controlled portions of a suitable diet.
  • Monitor growth, behaviour and compatibility.

Pairs perfectly with

  • A reliable water test kit.
  • Species-appropriate food.
  • Water conditioner.
  • Suitable plants, caves or cover.
  • A quarantine or observation setup where appropriate.
NTA Insight:
Check the adult animal, not only the size offered today. Adult size, social needs and behaviour are often the deciding factors.

Before You Buy

Compatibility: Confirm the exact product, variant, livestock and system compatibility before ordering.

Sizing: Use verified dimensions, actual aquarium volume and the intended application rather than relying on appearance alone.

Installation: Check access, placement, connections and safe operating requirements before use.

Replacement parts: Availability varies by product and manufacturer; confirm the exact model or SKU when a replacement is essential.

FAQ

How large do Red Dwarf Pencilfish grow?

Adults generally reach approximately 3–4 cm, making them suitable for smaller planted aquariums provided a proper group can be maintained.

How many should I keep?

We recommend at least six, with eight to ten or more preferred. Larger groups encourage more natural social behaviour and give males more opportunities to display.

Are males more colourful than females?

Yes. Mature males generally develop significantly stronger red colouration and may intensify dramatically during social displays. Females are usually more subdued and fuller-bodied.

Are Red Dwarf Pencilfish aggressive?

They are peaceful towards most tank mates. Males may establish small territories and display toward one another, but serious aggression is uncommon when sufficient space and cover are provided.

What should I feed them?

Their small mouths require appropriately sized foods. Fine micro pellets and crushed flakes work well as staples, supplemented with baby brine shrimp, daphnia and other small live or frozen foods.

Can they live with Apistogramma?

Yes. They can make excellent upper-level companions for peaceful Apistogramma in a properly sized South American aquarium. Their small size and preference for the upper water column complement dwarf cichlids very well.

Can Red Dwarf Pencilfish live with shrimp?

Adult shrimp generally coexist well with them, particularly in planted aquariums. Very small newborn shrimplets may still be eaten opportunistically.

Do they need blackwater?

No, but they are very well suited to soft, acidic blackwater-style aquariums containing driftwood, botanicals, floating plants and subdued lighting. Stable water quality remains more important than reproducing an exact tint.

What does Red Dwarf Pencilfish (Nannostomus mortenthaleri) do?

Red Dwarf Pencilfish (Nannostomus mortenthaleri) is intended for species-appropriate, established aquariums. Check the selected option and listing details against your needs.

What aquarium size is it suitable for?

Use any verified rating in the Specifications section as a starting point. If no rating is stated, contact NTA when tank size is the deciding factor.

Is this the right model for my aquarium?

Confirm purpose, physical fit, capacity and compatibility before ordering.

What's included in the box?

Only the selected product and components explicitly stated in the current listing are included.

Red Dwarf Pencilfish (Nannostomus mortenthaleri)

Available in store

Product form

Out of stock,  

$80.00  $40.00


All prices include GST
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    Description

    Red Dwarf Pencilfish (Nannostomus mortenthaleri)

    Tiny, elegant and intensely coloured, the Red Dwarf Pencilfish is one of the most beautiful nano fish available. Mature males develop brilliant crimson-red colouration contrasted by bold black lateral stripes and a fine golden sheen, creating a spectacular display in planted and blackwater aquariums. Peaceful, refined and highly sought after, Nannostomus mortenthaleri is a true feature species for aquarists who appreciate smaller fish with exceptional detail.

    Quick Facts

    • Brand: AI Livestock
    • Product type: Misc Fish
    • Size / Capacity: 4 cm
    • Suitable for: Species-appropriate, established aquariums

    Is this for you?

    ✔️ Perfect if:

    • Your aquarium is fully cycled and stable.
    • Adult size, social needs and compatibility have been checked.
    • You can provide the correct water conditions, diet and habitat.
    • You can receive and acclimate live livestock promptly.

    ❌ Consider something else if:

    • The aquarium is new, uncycled or unstable.
    • Compatibility or long-term space has not been confirmed.
    • You cannot meet the species-specific husbandry requirements.

    Why choose Red Dwarf Pencilfish (Nannostomus mortenthaleri)?

    It provides a clearly identified livestock option that can be assessed against your aquarium.

    Matching adult size, behaviour and water needs helps prevent avoidable stress.

    A planned addition is easier to acclimate, feed and monitor.

    It is preferable to a similar-looking species when its long-term needs better suit your setup.

    Key Benefits

    • Planned selection – Supports matching livestock to a suitable aquarium.
    • Aquarium suitability – Can become a rewarding part of a properly planned community.
    • Clear checks – Encourages confirmation of size, water and compatibility.
    • Long-term care – Keeps husbandry ahead of impulse selection.
    • Specialist support – NTA can help clarify suitability before ordering.

    Specifications

    • Capacity / Size: 4 cm
    • Shopify category: Live Animals

    Specifications may vary by model or manufacturer revision. Please check the selected variant where applicable.

    What's included?

    • The selected live livestock variant.
    • Protective packing appropriate to the available fulfilment method.
    • Care or acclimation guidance where supplied.
    • Only items explicitly stated in the listing are included.

    Setup & Use

    1. Prepare and test the aquarium before arrival.
    2. Inspect the package and follow current NTA acclimation guidance.
    3. Introduce the livestock calmly with reduced lighting where appropriate.
    4. Observe behaviour and compatibility closely.
    5. Maintain stable water and feed an appropriate diet.

    Maintenance

    Regular inspection and appropriate care help keep this product or livestock in suitable condition.

    • Test water regularly.
    • Maintain stable, species-appropriate parameters.
    • Feed controlled portions of a suitable diet.
    • Monitor growth, behaviour and compatibility.

    Pairs perfectly with

    • A reliable water test kit.
    • Species-appropriate food.
    • Water conditioner.
    • Suitable plants, caves or cover.
    • A quarantine or observation setup where appropriate.
    NTA Insight:
    Check the adult animal, not only the size offered today. Adult size, social needs and behaviour are often the deciding factors.

    Before You Buy

    Compatibility: Confirm the exact product, variant, livestock and system compatibility before ordering.

    Sizing: Use verified dimensions, actual aquarium volume and the intended application rather than relying on appearance alone.

    Installation: Check access, placement, connections and safe operating requirements before use.

    Replacement parts: Availability varies by product and manufacturer; confirm the exact model or SKU when a replacement is essential.

    FAQ

    How large do Red Dwarf Pencilfish grow?

    Adults generally reach approximately 3–4 cm, making them suitable for smaller planted aquariums provided a proper group can be maintained.

    How many should I keep?

    We recommend at least six, with eight to ten or more preferred. Larger groups encourage more natural social behaviour and give males more opportunities to display.

    Are males more colourful than females?

    Yes. Mature males generally develop significantly stronger red colouration and may intensify dramatically during social displays. Females are usually more subdued and fuller-bodied.

    Are Red Dwarf Pencilfish aggressive?

    They are peaceful towards most tank mates. Males may establish small territories and display toward one another, but serious aggression is uncommon when sufficient space and cover are provided.

    What should I feed them?

    Their small mouths require appropriately sized foods. Fine micro pellets and crushed flakes work well as staples, supplemented with baby brine shrimp, daphnia and other small live or frozen foods.

    Can they live with Apistogramma?

    Yes. They can make excellent upper-level companions for peaceful Apistogramma in a properly sized South American aquarium. Their small size and preference for the upper water column complement dwarf cichlids very well.

    Can Red Dwarf Pencilfish live with shrimp?

    Adult shrimp generally coexist well with them, particularly in planted aquariums. Very small newborn shrimplets may still be eaten opportunistically.

    Do they need blackwater?

    No, but they are very well suited to soft, acidic blackwater-style aquariums containing driftwood, botanicals, floating plants and subdued lighting. Stable water quality remains more important than reproducing an exact tint.

    What does Red Dwarf Pencilfish (Nannostomus mortenthaleri) do?

    Red Dwarf Pencilfish (Nannostomus mortenthaleri) is intended for species-appropriate, established aquariums. Check the selected option and listing details against your needs.

    What aquarium size is it suitable for?

    Use any verified rating in the Specifications section as a starting point. If no rating is stated, contact NTA when tank size is the deciding factor.

    Is this the right model for my aquarium?

    Confirm purpose, physical fit, capacity and compatibility before ordering.

    What's included in the box?

    Only the selected product and components explicitly stated in the current listing are included.

    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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