Product Details

Spotted Blue-Eye Rainbowfish – Pseudomugil gertrudae “Aru IV”

Overview:

The Spotted Blue-Eye Rainbowfish “Aru IV” is a small, delicate and beautifully patterned blue-eye rainbowfish with bright blue eyes, spotted fins and lively display behaviour. This locality form of Pseudomugil gertrudae is ideal for peaceful planted aquariums, nano-style species setups and carefully chosen small community tanks. It is not a boisterous fish, but in a mature aquarium with a good-sized group, fine foods and gentle filtration, males show superb fin displays and shimmering colour.

Key Identification:

Common Name: Spotted Blue-Eye Rainbowfish
Other Names: Gertrude’s Blue-Eye, Spotted Blue Eye, Aru IV Blue-Eye, Delicate Blue-Eye, Northern Blue-Eye
Scientific Name: Pseudomugil gertrudae “Aru IV”
Fish Type: Blue-eye Rainbowfish / Pseudomugil
Water Type: Freshwater

Natural Range & Habitat:

The wider species, Pseudomugil gertrudae, is native to northern Australia, southern New Guinea and the Aru Islands. FishBase describes it from small creeks, swampy marshes, shaded rainforest streams, lily lagoons and backwaters, often among dense vegetation, submerged log debris and muddy-bottomed Pandanus-lined creeks.

The Aru IV form is a locality strain from the Aru Islands region of Indonesia. The original species was described from Trangan Island in the Aru Islands, and locality forms from this region are especially valued by blue-eye enthusiasts for their pattern and display quality.

Appearance & Adult Size:

Spotted Blue-Eyes are small, slim fish with translucent to pale golden bodies, bright reflective blue eyes and ornate fins marked with black spotting or edging. Males are more colourful and develop larger, more decorative dorsal, anal and pelvic fins, which they flare during courtship and rivalry displays. Females are smaller-finned and more understated, but they are essential for natural behaviour.

Adults usually reach around 3–4 cm, with Aru forms often appearing a little larger and more robust than some other localities. Trade listings for Pseudomugil gertrudae “Aru IV” commonly give an adult size of up to around 4 cm.

Aquarium Suitability:

This is a lovely fish for a mature planted aquarium with calm tank mates. It suits fine-leaved plants, mosses, floating plants, botanicals, gentle flow and open swimming areas near the front and middle of the tank. Because of its small size and delicate fins, it should not be kept with large, aggressive or very boisterous species.

A species aquarium or a peaceful planted community is ideal. It is also a good choice for aquarists interested in breeding small rainbowfish, as it is an adhesive egg-layer that may spawn among mosses, fine plants or spawning mops.

Recommended Aquarium Size:

A practical minimum is 45–60 litres for a small group, with 70 litres or more preferred for a stronger shoal and better male display behaviour. A larger footprint gives more room for males to display and reduces pressure on females.

Water Conditions:

Temperature: 23–28°C
pH: 6.0–7.5
Hardness: Soft to moderately hard; adaptable if stable
Additional Notes: Provide clean, stable water and avoid immature aquariums. FishBase records wild P. gertrudae from waters around 23–30°C and pH 5.2–6.7, while aquarium-bred Aru IV stock is often kept successfully across a broader pH range if changes are gradual. Gentle filtration is best; avoid strong currents that constantly push these small fish around.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Spotted Blue-Eye Rainbowfish are peaceful, social and best kept with other small, gentle fish. Suitable tank mates include small rasboras, Ember Tetras, small pencilfish, peaceful microdevario-type fish, Otocinclus, small Cory-type catfish suited to the same water, and small shrimp only with caution.

Avoid angelfish, larger tetras, barbs, aggressive dwarf cichlids, fin-nippers, large gouramis and fast-feeding species that may outcompete them. Adult shrimp are usually safe, but tiny shrimplets may be eaten. Keep in a group of at least 8, with 10 or more strongly preferred. A mixed-sex group gives the best displays, but keep enough females so males are not constantly harassing just one or two fish.

Feeding:

This species needs small foods. Offer quality micro pellets, finely crushed flakes and powdered or granulated foods as the staple. Supplement regularly with frozen or live daphnia, cyclops, baby brineshrimp, microworms, small mosquito larvae and finely chopped bloodworm. Fine live or frozen foods are especially useful for conditioning males and encouraging spawning behaviour.

Because they are small and feed near the upper and middle levels, make sure food is fine enough and not taken immediately by larger tank mates.

Behaviour in the Aquarium:

Males are active display fish, flaring their fins, circling females and sparring with rival males without usually causing damage. They spend much of their time in the upper and middle levels, weaving among plants and open spaces. In a settled group, males display frequently, especially in the morning or after small water changes. They may jump if startled, so a secure lid is recommended.

Care Notes:

Add only to a mature, stable aquarium with low nitrate and gentle filtration. Avoid rough handling, aggressive tank mates and sudden water changes. Floating plants, mosses and fine-leaved plants make the fish feel secure and provide useful spawning sites. This species can be relatively short-lived compared with many larger aquarium fish, so maintaining a healthy group and allowing natural spawning can help keep the line going in established aquariums. Seriously Fish notes that P. gertrudae should not be added to biologically immature tanks and is best maintained in well-planted setups.

Recommended For:

Beginner to intermediate

Availability:

Occasional / Specialist locality strain / Often captive-bred

Image Disclaimer:

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Natural variation in size, colour, pattern and markings can occur between individual fish.