FishFreshwaterIntermediate
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Celebes Rainbowfish
Marosatherina ladigesi
The ethereal 'Celebes Rainbowfish' (8 cm). A gem from the island of Sulawesi, famous for its almost transparent glassy body crossed by a turquoise lightning bolt and for the extraordinary black extensions of the male fins. It is a demanding fish, requiring surprisingly hard and alkaline waters (similar to African cichlids) and tolerates thermal and chemical shocks very poorly.
Water Temperature
24 - 28 °C
pH Value
7 - 8
Water type
Freshwater
Tank level
Middle
Adult size
7 cm
Minimum tank volume
100 L
Minimum group
>= 1
GH
10 - 20 dGH
KH
5 - 10 dKH
TDS
200 - 400 ppm
Conductivity
313 - 625 uS/cm
Species description
Geographical Origin and Habitat: Endemic to the island of Sulawesi (formerly Celebes) in Indonesia. It inhabits forest streams characterized by moderate to fast currents, clear alkaline waters, and rocky or gravelly substrates. They are often found in shaded areas created by dense overhanging bank vegetation and trees.
Taxonomy and Morphology: Belongs to the family Telmatherinidae, genus Telmatherina. It is a small fish, reaching a maximum length of about 6-8 cm (2.5-3 inches). The body is slender and compressed. Its primary morphological feature is the presence of two separate dorsal fins, with the first rays of the second dorsal and anal fins in males extending into long, black and yellow filaments.
Social Behavior: An active, peaceful, and fast-swimming schooling fish. It must be kept in groups of at least 6-8 individuals, preferably with more females than males. Within the school, males perform spectacular courtship displays, extending their long fins to impress females and challenge rivals without physical harm.
Coloration and Sexual Dimorphism: The body has a translucent yellow-olive base color with a brilliant neon blue or greenish-blue stripe running along the lateral line from mid-body to the tail. The fins are colored bright lemon yellow with black edges. Sexual dimorphism is distinct: males are larger, have much longer, thread-like fins, and show more intense colors than females.
Care, breeding and tankmates
Aquarium Setup: Requires a tank of at least 100 liters (26 gallons) to allow a school room for free swimming. The layout should include open swimming space in the center, with dense plantings (such as Vallisneria and fine-leaved plants) along the sides and back for shelter. A dark substrate highlights their colors, and filtration should create moderate water movement.
Diet and Feeding: An omnivorous species that feeds on small insects falling on the water surface, insect larvae, and algae. In the aquarium, they accept high-quality dry flakes or micro-granules, but their diet should be regularly supplemented with live or frozen foods like brine shrimp, daphnia, and bloodworms to maintain color and trigger breeding.
Water Quality: Very demanding regarding water chemistry; they require hard and alkaline water. The pH must be maintained between 7.5 and 8.5, with a general hardness (GH) between 10 and 20 dGH and a temperature between 23°C and 28°C (73°F - 82°F). They are highly sensitive to nitrate accumulation and sudden water chemistry changes; weekly 20% water changes are essential.
Compatibility and Cohabitation: Excellent community fish with calm tankmates of similar size that share their preference for alkaline water. Good companions include other small rainbowfish, loaches, small loricariids, or Oryzias species. Avoid aggressive fish or fin-nippers that might damage the males' delicate fin extensions.
Aquarium Breeding: Spawning is possible in dedicated setups. The breeding tank should have fine-leaved plants or a yarn spawning mop. The pair deposits a few adhesive eggs daily over several days. Because adults will eat the eggs, it is best to remove the mop or plants daily to a separate hatching container with identical water parameters.
Risks and Diseases: Highly susceptible to bacterial infections and white spot disease (Ichthyophthirius) if stressed during transport or kept in soft, acidic water. Parameter stability and low organic waste levels are the best preventative measures.
Geographic Origin and Distribution
Endemic to the island of Sulawesi (formerly Celebes) in Indonesia. It inhabits forest streams characterized by moderate to fast currents, clear alkaline waters, and rocky or gravelly substrates. They are often found in shaded areas created by dense overhanging bank vegetation and trees.
Origin
Tropical oceans and reefsAfrica and MadagascarSouth and Southeast Asia
Fish profile
- Temperament
- Semi-aggressive
- The Celebes Rainbowfish is lively, highly active, and generally very peaceful. The males frequently engage in beautiful, harmless sparring displays where they flare their fins at one another to establish hierarchy. They are somewhat timid when first introduced, but become quite bold once they settle into a suitably sized school. Their energetic swimming behavior adds a wonderful dynamic element to the upper levels of any peaceful community tank.
- Diet
- Omnivore
- In the wild, they are micropredators that feed on small insects, larvae, and tiny crustaceans near the water surface. In the home aquarium, they eagerly accept high-quality micro-pellets and crushed flakes as their staple diet. To promote their best colors and breeding behavior, it is highly recommended to supplement their diet with live or frozen foods like Daphnia, baby brine shrimp, and cyclops. Since they have relatively small mouths, ensure all food particles are appropriately sized.
- Life expectancy
- 3-5 years
- In captivity, the Celebes Rainbowfish typically has a lifespan of 3 to 5 years when kept in optimal conditions. Providing them with stable, hard, and alkaline water parameters is essential to prevent stress and disease, which can shorten their life. A high-quality, varied diet and maintaining them in a school also contribute significantly to their overall health. Proper aquarium maintenance, including regular water changes, is crucial to prevent nitrate accumulation, which they are sensitive to.
- Adult size
- 7 cm
- The catalog's scalar value is 7 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 8 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Marosatherina ladigesi (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- School
- It is highly recommended to keep more females than males within the school to prevent excessive harassment. Males spend a great deal of time displaying their elaborate fins to attract females and establish dominance among themselves. A ratio of two females for every male is ideal for keeping the group dynamics peaceful and stress-free. If there are too many males, the constant competition can lead to exhaustion and torn fins.
- Feeding frequency
- Twice daily
- Because of their active nature and small stomachs, they benefit most from two or three small feedings per day. Provide only what the school can actively consume within a couple of minutes to prevent water fouling. They generally feed from the surface or mid-water column, so foods that sink too quickly might be ignored once they hit the substrate. A varied feeding schedule will help maintain their high energy levels and vibrant yellow and blue hues.
- Bioload
- The Celebes Rainbowfish has a relatively low bioload compared to heavier-bodied community fish. They are small, slender, and highly active, meaning their waste production is quite manageable in a well-filtered aquarium. However, since they must be kept in schools of at least six individuals, the cumulative bioload should be accounted for. Regular maintenance and a mature biological filter will easily process the minimal waste they generate.
- Flow
- Stagnant
- Marosatherina ladigesi naturally inhabits slow-moving streams and estuaries in Sulawesi, often in areas with clear water. They appreciate a moderate water flow that provides some current to swim against without being overpowering. Good oxygenation is important, so a filter return that creates gentle surface agitation is ideal. Avoid creating a true river-manifold system, as excessively strong currents will cause them undue stress and exhaustion.
- Reproduction
- Oviparous
- Breeding the Celebes Rainbowfish requires a dedicated setup with slightly hard, alkaline water and plenty of fine-leaved plants or spawning mops. They are continuous spawners, releasing a few eggs each day over a period of weeks. The adults may eat the eggs or the tiny fry, so it is best to move the spawning medium to a separate rearing tank every few days. The fry are incredibly small upon hatching and require infusoria or specialized liquid fry food before they can accept baby brine shrimp.
- Compatibility & tankmates
- This is a remarkably peaceful species that makes a wonderful addition to a community aquarium. They are best kept with other small, gentle fish such as rasboras, small tetras, corydoras, and smaller gouramis. Aggressive, boisterous, or fin-nipping tank mates must be avoided, as the delicate fins of the male Celebes Rainbowfish can easily be damaged. They also coexist quite well with peaceful invertebrates like Amano shrimp or snails.
- Tank level
- Middle
- This species predominantly occupies the middle and upper levels of the aquarium. They are extremely active and spend their days constantly cruising in the open swimming spaces looking for food. They rarely venture down to the substrate, making them perfect companions for bottom-dwelling fish. It is important to leave plenty of open water at the top of the tank while planting the edges densely for cover.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.1 ± 0.3 se
- Phylogenetic uniqueness (PD50)
- 1
- Bayesian Length-Weight
- a = 0.01122, b = 3.04
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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