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Spotted Blue-eye

Pseudomugil gertrudae

A charming freshwater rainbowfish native to Australia and New Guinea, celebrated for the males' elaborate spotted fins and bright blue eyes.

Taxonomy

Class:Actinopteri

Order:Atheriniformes

Family:Pseudomugilidae

Genus:Pseudomugil

Species:Pseudomugil gertrudae

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Water Temperature

22 - 28 °C

pH Value

6 - 7.5

Water type

Freshwater

Tank level

Surface and middle

Adult size

4 cm

Minimum tank volume

>= 30 L

Minimum group

5 - 12 dGH

2 - 6 dKH

TDS

95 - 240 ppm

Conductivity

148 - 375 uS/cm

Species description

Geographical Origin and Habitat: Pseudomugil gertrudae, commonly known as the spotted blue-eye, is native to the northern regions of Australia and southern parts of New Guinea. It inhabits shallow, calm freshwater bodies, such as swamps, billabongs, slow-flowing forest streams, and floodplains rich in submerged vegetation, floating plants, and decaying leaf litter.

Taxonomy and Morphology: It belongs to the family Pseudomugilidae. It is a small fish, reaching a maximum length of about 3 to 4 centimeters in adulthood. The body is partially translucent and elongated. Adult males develop exceptionally large, sail-like dorsal, anal, and pectoral fins decorated with distinct dark spots and brightly colored margins.

Social Behavior: It is a peaceful, schooling species that must be kept in groups of at least 10 or more individuals. This grouping not only reduces stress but also encourages males to engage in continuous and stunning courtship displays, raising and flaring their fins to establish dominance and attract females for spawning.

Coloration and Sexual Dimorphism: The coloration is magnificent: the body ranges from pale yellow to semitranslucent gold, covered with a dark scale outline that forms a checkered pattern. The males' fins are adorned with round black spots and white or yellow highlights. The eyes are a luminous, bright blue. Females have short fins and much duller coloration.

Care, breeding and tankmates

Aquarium Setup: Requires an aquarium of at least 50-60 liters for a school. The setup must include dense aquatic vegetation with plants like java moss, water ferns, and floating plants to diffuse the light. A dark substrate and natural driftwood create a comfortable environment that stimulates the fish's natural behaviors.

Diet and Feeding: Omnivorous diet. Because they have very small, upturned mouths, they require food of appropriate size. In the aquarium, feed small live or frozen foods such as baby brine shrimp, copepods, daphnia, microworms, and high-quality powdered or micro-pellet foods, administered in small daily portions.

Water Quality: Water parameters must be kept stable: optimal temperature between 21°C and 28°C, pH between 6.0 and 7.5, and soft to moderate water hardness (GH 5-15). It prefers gentle water filtration, as it does not like strong currents that can exhaust it during daily swimming. Regular small water changes are essential.

Compatibility and Cohabitation: It is an ideal fish for species-only setups or community aquariums with small, peaceful tankmates like freshwater shrimp (Neocaridina spp.), micro rasboras, pencilfish, pygmy corydoras, and other blue-eyes. Avoid larger or aggressive fish that could easily injure this delicate species or view it as prey.

Aquarium Breeding: Breeding in the aquarium is relatively easy and occurs daily under optimal conditions. They deposit a few adhesive eggs daily among mosses or spawning mops. The parents do not care for the eggs and may eat them; it is recommended to move the spawning mops to a separate hatching container for successful rearing.

Risks and Diseases: The primary risks include high sensitivity to sudden changes in water parameters and temperature, which can lead to osmotic shock and bacterial infections. Due to their relatively short lifespan (often under two years in captivity), it is important to purchase young specimens and maintain excellent tank hygiene.

Geographic Origin and Distribution

Pseudomugil gertrudae, commonly known as the spotted blue-eye, is native to the northern regions of Australia and southern parts of New Guinea. It inhabits shallow, calm freshwater bodies, such as swamps, billabongs, slow-flowing forest streams, and floodplains rich in submerged vegetation, floating plants, and decaying leaf litter.

Origin

Africa and MadagascarAustralia, New Guinea, and Oceania

Fish profile

Temperament: Semi-aggressive
Diet: Omnivore
Sex ratio: Harem
Feeding frequency: Twice daily
Bioload: Spotted Blue-eyes have a minimal bioload due to their tiny size. They are excellent candidates for small nano tanks. Pristine water conditions are essential for their health.
Flow: Stagnant
Reproduction: Oviparous
Compatibility & tankmates: They are incredibly peaceful and timid. They should only be kept with other diminutive, docile species or peaceful dwarf shrimp. Larger, boisterous fish will easily outcompete and stress them.
Tank level: Top/Middle

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level: 3.3 ± 0.4 se
Phylogenetic uniqueness (PD50): 0.5
Bayesian Length-Weight: a = 0.01122, b = 3.04

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

Recommendations grouped by close relatives, companion choices, and similar care.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Red Neon Blue-eye

Pseudomugil paskai

Species description

Care, breeding and tankmates