A school of the peaceful (but very energetic!) Australian Rainbowfish will make a dazzling display in a larger show tank!

The Australian Rainbowfish Melanotaenia fluviatilis is so named because it is indigenous to Australia. But it is also known by variety of other names including Murray River Rainbowfish, Crimson-spotted Rainbowfish, or Inland Rainbowfish. This species quickly demonstrates the appeal of the rainbow fish family. Males are brilliantly colored, with bold fin patterns and bright contrasting colors.

Their disposition is peaceful but with energy, making the Australian Rainbowfish a perfect inhabitant for a larger tank. With frequent water changes and the company of the opposite sex, males will show their intense colors off best. A planted tank is an excellent way to showcase your beautiful specimens. A school of these fish will certainly brighten up any aquarium.

These fish are great for the beginning fish keeper. They are very tolerant of temperature and water changes. The Rainbow fish are very hardy and normally able to fight off most disease. They will react well to medicine if needed. This fish is fairly easy to breed as well. They will make a beautiful and entertaining addition to your tank.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

Australian Rainbow Fish Spawning

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Long video capturing a pair of Australian Rainbow Fish during the spawning ritual!

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Atheriniformes
  • Family: Melanotaeniidae
  • Genus: Melanotaenia
  • Species: fluviatilis
Australian Rainbowfish – Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Size of fish – inches: 4.0 inches (10.16 cm)
  • Minimum Tank Size: 30 gal (114 L)
  • Temperament: Peaceful
  • Aquarium Hardiness: Very Hardy
  • Temperature: 70.0 to 79.0° F (21.1 to 26.1&deg C)
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Habitat: Distribution / Background

The Australian Rainbowfish Melanotaenia fluviatilis was described by Castelnau in 1878. They are indigenous to water systems of Australia typically inhabiting rivers, streams, ditches, swamps, and ponds where the water is relatively still and clear, but with thick vegetation. They tend to congregate in schools around logs and grassy riverbanks. They are omnivores, but feed mainly on small insects and crustaceans in the wild. Other common names they are known by include Murray River Rainbowfish, Crimson-spotted rainbowfish, and Inland Rainbowfish

The areas that they live in normally have high pH of 8+ but migrate to lower pH areas of around 6. They also live in a climate that has season changes, with the water temperature ranging from the high 70’s to the low 60’s. This makes them a very adaptable fish. Although they are not currently on the IUCN red list, they have faced a sharp population decline in the wild, especially noted during winter droughts.

  • Scientific Name: Melanotaenia fluviatilis
  • Social Grouping: Groups – They swim in schools, and will congregate in groups around logs and grassy riverbanks.
  • IUCN Red List: NE – Not Evaluated or not listed


The Australian Rainbowfish has a slender body with an arched back and narrow head. The eyes are relatively large and two dorsal fins are present. The base body color is an olive green or bluish brown, sometimes with a dark horizontal stripe mid body. The belly is rosy pink. There are rows of scales that reflect turquoise and green, and between the scales a thin reddish stripe can sometimes be seen. These colors are most likely to be seen in adult males. The fins are clear to reddish. Along the margin of the male’s dorsal and anal fin as well as the front margin of the pelvic fins may show an outline of black, especially when in breeding colors.

Female coloration is a muted version of the males. When in breeding mode the Male’s body color intensifies, becoming an emerald green. It should be noted that the river from which the fish genetically originates may cause significant variations in color.

  • Size of fish – inches: 4.0 inches (10.16 cm)
  • Lifespan: 5 years – Can have a lifespan of 5 to 8 years when kept in a well maintained aquarium.

Fish Keeping Difficulty

The naturally harsh, changing environments that these fish survive in, makes it a great fish for the new fish keeper. They are extremely tolerant to water condition changes and normally can fight off most aquarium diseases.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

The Australian Rainbowfish is an omnivorous species, but primarily feeds on aquatic invertebrates and terrestrial arthropods that fall into the water in its natural habitat. In captivity this fish requires a well planned diet for good health and coloration. About 60 – 75% of the diet should consist of a high quality processed food, appropriate for an omnivorous fish of this size. The rest of the diet should consist of live foods. Some good live food options include white worms, blood worms, or brine shrimp. If these are unavailable, frozen (defrosted) substitutes would be fine. These fish should be fed 2-3 times a day and only what they can consume in less then 5 minutes.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day – Feed two to three times daily, but give them only what they can consume in less than 5 minutes.

Aquarium Care

Rainbowfish are not exceptionally difficult to care for provided their water is kept clean. At least 25 – 50% of the tank water should be replaced weekly, especially if the tank is densely stocked. Because they are very active swimmers it is also advisable to keep these Rainbowfish in a tank at least 30 inches long and ideally 30 or more gallons. Additionally, the tank should be securely covered as these fish are skilled jumpers and will probably do so if given the opportunity.

  • Water Changes: Weekly – Weekly water changes of at least 20-30%, more if the tank is densely stocked.

Aquarium Setup

Rainbow fish will do best and are most effectively displayed in tanks which simulate their natural habitat. A sandy substrate, dense vegetation, and bog wood all echo the native rivers of the Australian Rainbowfish. Try, if possible, to plan for one or two hours of sunlight hitting the tank. This should be at a time when you can view the tank as the illumination will make the fish even more stunning.

As with most of the Rainbowfish species they are most at home in well planted aquariums. When you choose plants make sure to pick plant that can tolerate the hard, alkaline conditions preferred my this fish. They also need stretches of open swimming areas. An efficient filter and good water movement are needed for the male fishes to develop their coloration.

  • Minimum Tank Size: 30 gal (114 L)
  • Suitable for Nano Tank: Yes
  • Substrate Type: Small Gravel
  • Lighting Needs: Moderate – normal lighting
  • Temperature: 70.0 to 79.0° F (21.1 to 26.1&deg C)
  • Breeding Temperature: 72.0° F
  • Range ph: 6.5-8.5
  • Hardness Range: 8 – 25 dGH
  • Brackish: No
  • Water Movement: Any
  • Water Region: All – Australian Rainbowfish will school in the top or middle of the tank.

Social Behaviors

Australian Rainbowfish do fine in a community aquarium of similarly sized fish, but do exceptionally well in a geographical tank stocked with other rainbow fish. Although generally non-aggressive, overly aggressive or very shy tank mates will make bullies out of them. Mix them with other playful but good natured fish for best results. You may notice some chasing between rainbowfish, but this is rarely a concern unless a fish is injured, has nowhere to hide, or is constantly harassed (usually a result of one of the first two).

Australian Rainbowfish must be kept in schools of six or more, and good gender ratios are important to keep a reasonable peace among them. Although you can always keep single sex schools, you will see significantly better coloration if both genders are in the tank. Properly stocking rainbow fish is a little tricky so we include the following recommendation for stocking. Choose which type of school you want to keep and how many fish.

If you wish to keep…

  • 5 rainbowfish – Do not mix sexes
  • 6 rainbowfish – 3 males + 3 females
  • 7 rainbowfish – 3 males + 4 females
  • 8 rainbowfish – 3 males + 5 females
  • 9 rainbowfish – 4 males + 5 females
  • 10 rainbowfish – 5 males + 5 females

If putting your Rainbow fish in a community tank, provide ample hiding spots for these fish. With out the comfort of being able to find shelter it is unlikely to get the most of their coloration. In nature you will find them in schools under floating logs and plants when not swimming as a group, they need the same enviromnent in the aquarium.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Yes – Likes groups of 6 or more.
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Monitor – Rainbowfish are wild fast swimmers so can make slower fish nervous and stressed.
    • Shrimps, Crabs, Snails: May be aggressive – Larger ornamental shrimps and crabs will be fine, but as their natural diet in the wild consists of small crustaceans and invertebrates, these could be at risk.
    • Plants: Safe

Sex: Sexual differences

Mature males will be more colorful and have a more highly arched back.

Breeding / Reproduction

A breeding tank should be set up with a sponge filer and either many fine leaved plants or a spawning mop. A pair of healthy adult rainbow fish should be introduced. They should be conditioned with live foods and plant based foods. Remember, you are trying to emulate the bounty of the flood season so feed more and higher quality food than you normally would.

After the female has produced eggs, the males will display an amazing show of intense colors and direct the female to the spawning site, spawn, and then rest. The spawning mop or plants should be removed and replaced after the spawning or the eggs will be eaten. The fish will repeat this daily for a few days, with steadily decreasing numbers of eggs produced. The parents should be removed when egg numbers fall or if the females show signs of fatigue.

The fry will hatch after about a week and should be fed infusoria or a liquid fry food until they are able to eat small live foods. The fry are something of a challenge to raise until they are about two months old. The fry grow slowly and require clean water during the entire process.

A problem to be aware of is crossbreeding. Rainbowfish in the wild will not breed with fish of another species, even when presented the opportunity to do so. But for some reason, rainbowfish of the Melanotaeniidae family in the aquarium will interbreed, often with undesirable results. Somehow the fry of mismatched parents lose most of their coloration. Since many of these species are rare, it is desirable to keep the bloodlines distinct, or risk losing the beautiful coloration that nature has taken thousands of years to develop. See an overview of how to breed Rainbow fish in Breeding Freshwater Fish.

  • Ease of Breeding: Moderate

Fish Diseases

Rainbowfish are extremely hardy and disease is not usually a problem in a well maintained aquarium. That being said there is no guarantee that you won’t have to deal with health problems or disease. Remember anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so not to upset the balance.

A good thing about rainbow fish is that due to their resilience, an outbreak of disease can often be limited to just one or a few fishes if you deal with it at an early stage. When keeping more sensitive types of fish, it is common for all fishes to be infected even before the first warning signs can be noticed. The best way to proactively prevent disease is to give your Rainbow fish the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. Stressed fish are more likely to acquire disease.

For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments. This is a great source for information on disease and treatments. It is recommended to read up on the common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. Rainbow fish are very resilient.


The Australian Rainbowfish, also sold as the Murray River Rainbowfish or Inland Rainbowfish, are somewhat rare. You may be able to special order them from your local fish store or locate them online. They are moderately priced.


 Murray River Rainbow Fish (Image Credit: Bahudhara, Wikimedia Commons CC BY-SA 3.0 Unported)