Telmatherinidae

Sulawesi Rainbowfish

Marosatherina ladigesi

Marosatherina ladigesi, known as Ladiges's Telmatherina, or "Sunbeam" Rainbowfish, as well as Sulawesi Rainbowfish, belongs to the family Telmatherinidae. This fish stands out for its vibrant coloration, peaceful disposition, and ease of care. These qualities make it an excellent inhabitant for a home tropical aquarium.

Tank
from 70 L (18 gal)
Temperature
22 – 28 °C (72 – 82 °F)
Size in aquarium
8 cm (3.1 in)
Acidity
pH 7–8
Natural rangeRange on the map
  • Sulawesi area
  • Indonesia

Tank conditions

Plan the tank stocking
Temperature
22 – 28 °C (72 – 82 °F)
Water pH
Neutral (7) – Slightly alkaline (8)
Water dH
Medium hardness (10) – Very hard (25)
Water salinity
no salt (freshwater)
Size in aquarium
8 cm (3.1 in)
Lifespan
4 years
Temperament
Peaceful (regular)
Toward small fish
not a predator
Required aquarium volume
from 70 L (18 gal)
Lighting
dimmed
Substrate
any (no restrictions)
Water flow
weak
Swimming level
middle level
Feeding
Any (universal)
Keeping
Medium group 6–8 individuals
Jumping
low
  • Lifespan. A lifespan to expect under good care, not a measured value: it depends heavily on tank volume, water quality and diet — and for selectively bred forms, on their origin as well.
  • Toward small fish. Based on the Predators category in the catalog or the temperament in the species parameters. “A risk to small fish” means the species is not a predator by habit, yet will swallow any fish that fits in its mouth.
  • Required aquarium volume. This is a husbandry recommendation, not a measured value: the volume depends on the keeping mode (medium group (6–8 individuals)), footprint, decor and tank mates.

Care and keeping

Description

Adults of this species reach up to 8 cm in length. Their bodies are olive-colored, while the fins are bright yellow, and a striking blue line runs along the entire length of the body from tail to head. Males differ from females by their more intense coloration and noticeably larger fins.

Habitat

This species is endemic to Sulawesi Island in Indonesia. These fish inhabit clear, small rivers that flow down hillsides covered with lush tropical forests.

Behavior and Compatibility

This calm and peaceful species coexists well with other fish of similar size and temperament, provided they can inhabit a similar environment. It is recommended to keep them in schools of at least 6–8 individuals, with a ratio of 1 male to 2–3 females.

Care and Maintenance

For a small school of these fish, an aquarium of at least 70 liters will be required. The decor should include an abundance of floating and rooted plants, arranged in groups to leave sufficient open areas for free swimming. The choice of other decorative elements is at the discretion of the aquarist. Particular attention should be paid to maintaining high water quality. Weekly water changes of at least 25% of the volume, as well as the installation of an effective filtration system, are key conditions for the successful keeping of Sulawesi Rainbowfish. Contrary to a widespread belief, this species does not need salt added to its water, although it tolerates mildly brackish conditions.

Diet

The fish readily accept all types of popular foods, including dry, frozen, and live. A varied diet consisting of high-quality products will allow them to display the full beauty of their coloration. It is desirable to include live foods in their diet at least once a week, if possible.

Breeding and Reproduction

Breeding these fish in a home aquarium does not present significant difficulties. Their ability to reproduce offspring is maintained throughout the year. For successful spawning, it is important to provide thickets of fine-leaved or low-growing plants, as well as mosses; artificial alternatives are also suitable. The mating period lasts up to two weeks, during which the female lays portions of eggs daily. The eggs are attached to the surface of plants with thin adhesive threads. Notably, one male can fertilize several clutches from different females. Since these fish lack parental instincts, adult individuals often eat their own offspring. To save the fry, the eggs must be promptly removed from the main aquarium and carefully transferred to a separate tank where the water parameters are identical. To provide the necessary conditions in the new aquarium, a heater and a simple sponge air-lift filter will suffice. The fry emerge after 5–10 days, with this period depending on water temperature. In the initial stage of life, they will require micro-foods, such as infusoria; subsequently, they can transition to specialized powdered foods or Artemia nauplii.

Diseases

Health problems usually arise only as a result of injuries or keeping in unsuitable conditions, which leads to a weakening of the immune system and, as a rule, provokes the development of various diseases. At the first signs of illness, the primary task is to check the water parameters for excesses or dangerous concentrations of toxic substances (nitrates, nitrites, ammonia, etc.). After bringing all indicators back to normal, treatment can begin.

How to choose

When purchasing, choose active, lively individuals with clean fins and scales, free from visible damage or growths. Avoid fish showing signs of emaciation, sunken bellies, or unnatural behavior, such as constantly hovering at the bottom or attempting to stay separate from the school. As the species is sensitive to environmental quality, it is important to ensure that the store's aquarium maintains stable water parameters and cleanliness, and that the fish themselves do not appear stunted.

Compatibility

There are no pair reviews for this species yet — check tankmates in the matcher.

All tankmates

Plants and this fish

Matching water does not mean the plant will stay intact.

Frequently asked questions

The essentials: size, tank volume, water parameters and care

How big does Sulawesi Rainbowfish get?

An adult reaches 8 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Sulawesi Rainbowfish need?

The recommended volume is 70 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Sulawesi Rainbowfish need?

Temperature 22–28 °C, pH 7–8, hardness 10–25 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Sulawesi Rainbowfish live?

Around 4 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Sulawesi Rainbowfish aggressive?

Temperament: peaceful (regular). Keep this in mind when choosing tank mates.

How many Sulawesi Rainbowfish should be kept together?

Recommended setup: medium group (6–8 individuals). Ignoring this is a common cause of stress and disease.

What does Sulawesi Rainbowfish eat?

Diet type: any (universal). Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of Sulawesi Rainbowfish?

The scientific name of the species is Marosatherina ladigesi, family Telmatherinidae. It also appears in the literature as: Telmatherina ladigesi.

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Other scientific names and conservation status

Other scientific names
Telmatherina ladigesi
Categories
Rainbowfish
Conservation status
VulnerableVU