Marosatherina ladigesi (Celebes Sunray Fish)

22 June 2026

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The Celebes Sunray Fish, often known as the Celebes Rainbowfish, is a stunning, active schooling fish native to the clear, alkaline streams of Sulawesi, Indonesia. Admired for its striking neon blue lateral stripe and the male's dramatic, elongated fin extensions, it brings a vibrant, graceful energy to peaceful community aquariums.

Marosatherina ladigesi (Celebes Sunray Fish)

Overview

The Celebes Sunray Fish (Marosatherina ladigesi), frequently referred to in the aquarium hobby as the Celebes Rainbowfish, is a captivating and lively freshwater species. Known for their delicate, translucent bodies and brilliant flashes of neon blue, these fish are a favorite among aquarists looking to add movement and color to hard-water community tanks. While they require specific water parameters to truly thrive, their peaceful nature and stunning courtship displays make them well worth the effort.

Image of celebes sunray fish marosatherina ladigesi

Distribution and Habitat

Endemic to the island of Sulawesi (formerly known as Celebes) in Indonesia, this species is primarily found in the Maros karst region. They inhabit clear, slow-moving streams and rivers that run through limestone areas, which naturally buffers the water, making it hard and alkaline. These natural habitats are often shaded by dense rainforest canopies, providing a dappled light environment with plenty of submerged roots and vegetation.

Description of Celebes Sunray Fish

Body shape:

They possess a slender, elongated, and laterally compressed body typical of many rainbowfish and silversides, allowing them to dart quickly through the water.

Color:

The body is largely semi-transparent with a yellowish or golden tint. A brilliant, iridescent neon blue lateral stripe runs from the pectoral area to the base of the tail. The fins feature striking contrasts of black and vibrant yellow.

Barbels:

This species does not possess any barbels.

Snout:

They have a relatively pointed snout with a slightly upturned mouth, which is perfectly adapted for snatching small insects and food particles from the water's surface.

Eyes:

Their eyes are large and prominent, often featuring a highly reflective, iridescent blue or green ring around the pupil.

Fins:

They have two distinct dorsal fins. The males are particularly famous for their heavily elongated, filamentous second dorsal and anal fins, which trail gracefully in the water and are colored in striking black with yellow or white tips.

The Tail:

The caudal (tail) fin is deeply forked, with the upper and lower lobes distinctly edged in dark black and bright yellow.

Temper

The Celebes Sunray Fish is entirely peaceful. They do not bother other tank mates and are generally timid if kept with overly boisterous or aggressive species.

Sociality

This is a highly social, schooling fish. They must be kept in groups of at least six individuals, though groups of eight to ten or more are highly recommended. Keeping them in larger schools encourages natural behaviors, reduces stress, and prompts the males to show off their best colors as they harmlessly spar and display for the females.

Activity

They are very active swimmers, constantly on the move during daylight hours. They predominantly occupy the middle and upper levels of the water column.

Keeping and Caring for Celebes Sunray Fish

Tank size:

A minimum aquarium size of 20 gallons (approx. 75 liters) is required for a small school, but a 30-gallon tank or larger is ideal to provide them with the ample swimming space they crave.

Water Parameters:

Temperature

They thrive in tropical temperatures ranging from 22-28°C (72-82°F).

pH

Alkaline water is crucial for their long-term health. Maintain a pH between 7.0 and 8.0.

Hardness

They originate from limestone-rich streams and require moderately hard to hard water, ideally between 10 and 20 dGH.

Ammonia, Nitrite, Nitrate

Ammonia and Nitrite must always be at 0 ppm. Nitrates should be kept as low as possible (under 20 ppm). They are highly sensitive to poor water quality, so strict maintenance is necessary.

Lighting

Moderate lighting is best. While they look stunning under bright lights, providing some shaded areas with floating plants will make them feel more secure and mimic their natural forest stream habitat.

Water flow

A moderate water flow is appreciated, simulating the gentle currents of their native streams.

Decorations and Plants

A planted aquarium with plenty of open swimming space in the center is ideal. Use driftwood, rocks, and hardy plants like Vallisneria or Anubias. Darker substrates can help their neon colors stand out more vividly.

Diet

They are omnivorous micro-predators in the wild. In the aquarium, they will readily accept high-quality flakes and micro-pellets. To maintain their best health and coloration, supplement their diet with live or frozen foods such as daphnia, cyclops, baby brine shrimp, and mosquito larvae.

Some Feeding Tips

Because they have relatively small throats, ensure all food is appropriately sized. It is better to feed them small amounts two to three times a day rather than one large meal. They prefer to feed from the surface or as food sinks through the water column.

Breeding

Celebes Sunray Fish are continuous egg scatterers. To breed them, set up a dedicated breeding tank with slightly hard, alkaline water and provide spawning mops or dense, fine-leaved plants like Java Moss. Condition the adults with plenty of live foods. The females will scatter a few eggs daily, which the males will fertilize. The parents will eat the eggs if given the chance, so it is best to remove the eggs or the parents after a few days. The fry are extremely tiny upon hatching and will require infusoria or liquid fry food until they are large enough to accept freshly hatched baby brine shrimp.

Conclusion

The Celebes Sunray Fish is a magnificent, active species that brings a unique flash of neon color and elegant finnage to the home aquarium. While they demand specific hard-water parameters and pristine conditions, aquarists who meet their needs will be rewarded with a lively, peaceful, and visually stunning display.

Fish info

Care level: Moderate
Temperament: Peaceful
Adult size: 6-8 cm
Life expectancy: 3-5 years
Fish type: Rainbowfish
Temperature : 22-28°C
pH: 7.0-8.0
Color Form: Black, Blue, Clear, Yellow

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