How many Gertrude's Blue-Eyes should I keep together?

They are a shoaling species and feel most secure in groups. A minimum of 6 is required, but a group of 8 to 10 or more is ideal. Try to keep a ratio of one male to two females to reduce harassment.

Can I keep Pseudomugil gertrudae in a tank without a heater?

No. Despite being small, they are tropical fish native to warm climates. They require a stable water temperature between 21°C and 28°C to thrive and display properly.

Why are my blue-eyes ignoring their food?

Their mouths are incredibly small and face upwards. If the food you are offering is too large, or if it sinks too rapidly, they will not be able to eat it. Switch to micro-pellets, crushed flake, or live baby brine shrimp.

Are they safe to keep with cherry shrimp?

Yes, they are generally very safe with adult Neocaridina and Caridina shrimp. Their mouths are too small to harm adults, though they may opportunistically eat newly hatched shrimplets if they catch them in open water.

Why are my males not showing their spotted fins?

Males need the presence of females to trigger their courtship displays. Additionally, they require a heavily planted, secure environment and high-quality live or frozen foods to reach their full colour potential.

FreshwaterTropicalIntermediate

Gertrude's Spotted Blue-Eye

Pseudomugil gertrudae

A stunning, diminutive freshwater fish renowned for its striking blue eyes and the male's spectacular, spotted fin displays.

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Ideal Conditions

Temperature: 21 – 28 °C
pH range: 5 – 7.5
Hardness: 1 – 12 dGH
Adult size: 3 – 4 cm
Standard 45L nano or 60cm aquarium: 45 litres+
Lifespan: 1 – 3 years
Diet: Micro-predator
Water flow: Low to moderate
Preferred setup: Densely planted with floating vegetation, dark substrate, and driftwood/leaf litter.

About the Gertrude's Spotted Blue-Eye

Native to the heavily vegetated swamps and streams of Australia and Papua New Guinea, Gertrude's Spotted Blue-Eye is a highly sought-after species for nano aquariums. They are celebrated for their intricate beauty, despite their tiny size. Males are instantly recognisable by their dramatically elongated, spotted fins, which they flick continuously to attract mates in a captivating display of natural behaviour.

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Is it right for your tank?

Check Gertrude's Spotted Blue-Eye against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Gertrude's Spotted Blue-Eye comes from

Native range

Northern Territory, Cape York Peninsula, Fly River basin

Countries / regions

Australia, Papua New Guinea

Habitat

Shallow, heavily vegetated billabongs, slow-flowing forest streams, and swamp margins, often featuring tannin-stained water.

Several distinct location-specific morphs exist, such as 'Aru II' or 'Aru IV', which look slightly different and should ideally not be hybridised.

Similar species

Forktail Blue-Eye
Pseudomugil furcatus
Pacific Blue-Eye
Pseudomugil signifer
Red Neon Blue-Eye
Pseudomugil luminatus

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Pygmy Corydoras
Corydoras pygmaeus
Peaceful, diminutive bottom-dwellers that occupy a different water strata and will not compete aggressively for food.
Great
Cherry Shrimp
Neocaridina davidi
Excellent nano tank companions; adult shrimp are perfectly safe, though newly hatched shrimplets may occasionally be eaten.
Great
Chili Rasbora
Boraras brigittae
Similar in size and peaceful temperament, creating a harmonious and colourful micro-community.
Great
Guppy
Poecilia reticulata
Guppies are vigorous eaters and may outcompete the shy, small-mouthed blue-eyes for food.
Compatible with caution
Angelfish
Pterophyllum scalare
Angelfish will view adult blue-eyes as prey and effortlessly swallow them whole.
Not recommended

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