Spotted Blue-Eye Rainbowfish Aru (Pseudomugil Gertrudae)

The Spotted Blue-Eye Rainbowfish Aru refers to a specific and visually distinctive population of the species Pseudomugil gertrudae, originating from the Aru Islands in Indonesia. These small, peaceful fish are highly regarded in the aquarium hobby for their attractive colors and suitability for planted nano tanks.

Here are the key details about this fish:

• Scientific Name: Pseudomugil gertrudae 

• Common Names: Spotted Blue-Eye, Gertrude's Blue-Eye, Delicate Blue-Eye

• Variant Names: Often sold as "Aru II" or "Aru IV" to denote the specific island strain

 Origin and Natural Habitat

The species Pseudomugil gertrudae was first scientifically described in 1911 from specimens collected on Trangan Island in the Aru Islands, Indonesia. This is why the "Aru" variants are particularly significant.

In the wild, they are found across northern Australia, southern New Guinea, and the Aru Islands. Their natural habitat consists of slow-moving freshwater environments like small creeks, swampy marshes, and rainforest streams, often with muddy bottoms and dense vegetation like Pandanus palms.

 Appearance and Aru Variants

This is a very small fish, with adults typically reaching a maximum size of 3 to 3.8 cm (about 1.2 to 1.5 inches).

• General Description: The base body color is generally translucent to pale silver-white or yellowish. A key feature is the pattern of three horizontal black lines on the rear half of the body, which break into spots towards the front. Their fins are usually yellow with black markings, and their eyes are a striking, bright blue, which gives them their name.

• The "Aru" Difference: Importantly, body size and color vary across their geographic range. Fish from the Aru Islands are noted for being larger than other populations. The "Aru II" strain, in particular, is a selectively bred variant prized for its enhanced coloration. Males in this strain display extended, fan-like second dorsal and anal fins and develop a beautiful turquoise blue/silver sheen on their bodies and fins, contrasting with a yellowish head.

 Aquarium Care

These fish are peaceful and active, making them excellent community fish for small aquariums, provided their needs are met.

• Tank Setup: They thrive in well-planted tanks, ideally with a dark substrate to help bring out their colors. Floating plants are also appreciated as they mimic their shaded natural habitats.

• Water Parameters:

  • Temperature: 22 - 28°C (72 - 82°F)

  • pH: They are adaptable, but a range of 6.0 - 7.5 is ideal, though they can tolerate more acidic conditions found in the wild.

• Tank Size: A minimum of 60 litres (~15-20 gallons) is recommended for a small school, with larger tanks being better for stability and to showcase their behavior.

• Social Behavior: They are a schooling species and must be kept in groups of at least 6-8 individuals. In larger groups, males will display their best colors and courtship behaviors for each other. They are peaceful and can be kept with other small, non-aggressive fish and even adult dwarf shrimp, but they can be timid and may be outcompeted for food by faster tank mates.

 Diet and Feeding

As omnivores, they have a varied diet.

• In the wild, they eat algae and small invertebrates.

• In the aquarium, they will accept high-quality flake foods. However, to maintain optimal health and enhance their vibrant colors, their diet should be regularly supplemented with small live or frozen foods like brine shrimp (artemia), micro-worms, and daphnia.