Rainbowfishes (Melanotaeniidae)

Murray River Rainbowfish

Melanotaenia fluviatilis

The Murray River Rainbowfish, also known as the River Rainbowfish, bears the scientific name Melanotaenia fluviatilis and belongs to the family Melanotaeniidae. This fish is characterized by its unpretentiousness, ease of care, and simple breeding. Thanks to its beautiful coloration and compatibility with many other species, it will be an excellent choice for beginner aquarists.

Tank
from 85 L (22 gal), 100 L (26 gal) recommended
Temperature
20 – 25 °C (68 – 77 °F)
Size in aquarium
10 cm (3.9 in)
Acidity
pH 6.5–8
Natural rangeRange on the map
  • Queensland area
  • New South Wales area
  • Australia

Tank conditions

Plan the tank stocking
Temperature
20 – 25 °C (68 – 77 °F)
Water pH
Neutral (6.5) – Slightly alkaline (8)
Water dH
Medium hardness (8) – Very hard (20)
Water salinity
no salt (freshwater)
Size in aquarium
10 cm (3.9 in)
Lifespan
5 years
Temperament
Peaceful (regular)
Toward small fish
not a predator
Required aquarium volume
from 85 L (22 gal), 100 L (26 gal) recommended
Lighting
dimmed
Substrate
any (no restrictions)
Water flow
weak
Feeding
Any (universal)
Keeping
Medium group 6–8 individuals
  • 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 can reach up to 10 cm in length. Their coloration varies depending on the region of origin, often including iridescent blue, yellow, and greenish hues. One of their recognizable features is the dark edging on their fins and a reddish tint to their tail. Differences between sexes are moderately expressed: males are usually slightly larger than females and have more intense coloration.

Habitat

The natural habitats of this fish are located on the eastern coast of Australia, covering areas of Queensland and New South Wales. Rainbowfish are found in a wide variety of water bodies, such as rivers, ponds, lakes, and swamps. They prefer areas with slow currents where dense aquatic vegetation is present. The conditions of their habitat are subject to seasonal changes, which manifest in fluctuations in temperature and rainfall.

Behavior and Compatibility

This active and peaceful fish coexists well with other non-aggressive species of similar size. However, the excessive activity of the Southern Rainbowfish may be undesirable for slower tank mates, so it's best to exclude them from a community tank. It is recommended to keep them in a school consisting of at least 6–8 individuals of both sexes.

Care and Maintenance

For keeping a small group of these fish, an aquarium of at least 100 liters will be required. In terms of decor, it is advisable to alternate areas with dense vegetation and open spaces for active swimming. The addition of driftwood, which will serve as hiding places, is welcome. The choice of substrate depends on the requirements of the plants and the owner's preferences. A key aspect of successful keeping of the Murray River Rainbowfish is maintaining water cleanliness, so it is recommended to replace 15–20% of the water volume weekly with fresh water. In addition, an effective filtration system is necessary. The fish feels more comfortable with moderate lighting and does not tolerate strong internal currents. All these factors are important to consider when selecting and setting up aquarium equipment.

Diet

These fish are undemanding when it comes to feeding. They readily accept most common types of food, whether dry, live, or frozen. To ensure the best color display, it is desirable to combine different products. For example, flakes and granules can be alternated with bloodworms or Artemia.

Breeding and Reproduction

For successful breeding of rainbowfish, both a community tank and a specially prepared breeding tank can be used. Creating favorable conditions for the start of the breeding season involves maintaining the water temperature at 22–24°C, with the water being slightly alkaline (pH up to 7.5) and having medium hardness. In the aquarium setup, it is important to provide dense thickets of fine-leaved plants or their artificial counterparts; these will serve as a spawning substrate where females can lay their eggs. Spawning continues for approximately 2 weeks, during which the female daily produces several dozen eggs, and the male fertilizes them. Parental instincts are absent in these fish, so after spawning, they lose all interest in their future offspring. If breeding occurs in a community tank, it is recommended to move the eggs to a separate tank with similar conditions to avoid the risk of them being eaten by other inhabitants. In the absence of a separate breeding tank, abundant clusters of floating plants can be used. They will serve as a reliable refuge for fry, which in the first days of life stay near the water surface. The incubation period lasts from 6 to 10 days, depending on the temperature. In early life, fry feed exclusively on microscopic food, such as infusoria. After about a week, their diet can be supplemented with Artemia nauplii or specialized powdered foods designed for aquarium fish fry. It is important to note that feeding rainbowfish fry in a community tank presents certain difficulties, unlike in a separate breeding tank.

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 selecting individuals, pay attention to their activity and skin condition. Healthy fish should show curiosity, actively swim in a school, and have no visible damage, ulcers, or spots. Avoid purchasing fish with clamped fins, rapid breathing, or signs of emaciation, as these symptoms may indicate hidden diseases or stress from improper transportation conditions. It is recommended to prefer individuals with pronounced coloration characteristic of the species. Before purchasing, ask the seller about the keeping conditions in the store and, if possible, observe the feeding process to ensure there are no appetite problems.

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 Murray River Rainbowfish get?

An adult reaches 10 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Murray River Rainbowfish need?

The recommended volume is 100 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Murray River Rainbowfish need?

Temperature 20–25 °C, pH 6.5–8, hardness 8–20 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Murray River Rainbowfish live?

Around 5 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Murray River Rainbowfish aggressive?

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

How many Murray River Rainbowfish should be kept together?

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

What does Murray River 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 Murray River Rainbowfish?

The scientific name of the species is Melanotaenia fluviatilis, family Rainbowfishes (Melanotaeniidae). It also appears in the literature as: Aristeus fluviatilis, Melanotaenia splendida, Nematocentris fluviatilis.

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Other scientific names and conservation status

Other scientific names
Aristeus fluviatilis, Melanotaenia splendida, Nematocentris fluviatilis
Categories
Rainbowfish
Conservation status
Least concernLC