Aquariums, Freshwater fish, Information, Rainbowfish, Species

Australian rainbowfish (Melanotaenia fluviatilis)

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by Jason Matthews



Australian rainbowfish is a popular species among pet fish owners. With its bright and vibrant colors, it’s no surprise this species is a favorite among aquarium enthusiasts. This article will delve into the fascinating world of the Australian rainbowfish.

From its origin to its unique behaviors and ideal tank conditions, we will cover everything you need to know about this beautiful species. Whether you are a beginner or an intermediate pet fish owner, you will gain a comprehensive understanding of the Australian rainbowfish, making it easier for you to care for and appreciate this fantastic species.


Scientific Name: Melanotaenia fluviatilis (Melanotaeniidae)
Common Names: Rainbowfish
Life Expectancy: 5-8 years
Adult Size: 10.16 cm (4 inches)


HabitatRivers, streams, and lakes
Care LevelEasy
DietPrimarily omnivorous
Tank LevelMiddle to top
Minimum Tank Size20 gallons (75 liters)
Water pH6.5-8.0
Water Temperature72-82°F (22-28°C)
Water HardnessSoft to moderately hard water, 5-15 dGH
LightingModerate to high lighting
Tank MatesPeaceful community fish, avoid keeping with fin nippers or aggressive species

Fun Fact Corner

Did you know these fish have a unique adaptation that sets them apart from other fish species? These fish have a specialized lateral line system that detects vibrations and movements in the water, allowing them to respond to potential predators or prey quickly. This adaptation is significant for their survival in the fast-moving rivers and streams of their native habitat in Australia.


The Australian rainbowfish can be traced back to the waterways of northern and eastern Australia. They are native to the region’s rivers, streams, and billabongs, thriving in the warm, tropical climate. In their natural habitat, they play an important role in the ecosystem, providing food for larger predatory fish and aiding in maintaining the aquatic environment’s balance.

Appearance & Size

The Australian rainbowfish body is sleek and streamlined, with a metallic sheen that shimmers and shines in the light. They have a long and slender dorsal fin and an equally impressive caudal fin that fans out beautifully. The coloration of the Australian rainbowfish can range from bright orange, yellow, and red, to iridescent blue and green, depending on the variety.

The size of the Australian rainbowfish is relatively tiny, with most adults reaching a maximum length of 4 inches. This makes them ideal for smaller aquariums, as they only require a little swimming space.


The male Australian rainbowfish has more vibrant and pronounced colors than females, making it a relatively easy species to sex. Males have longer dorsal fins, a more defined overall body shape, and a rounded and plump appearance. Female Australian rainbowfish are more slender and less colorful, but they are still stunning in their own right. It is important to note that the species’ colors and patterns can change depending on their mood and surroundings, making it difficult to determine their gender solely by appearance.


The Australian rainbowfish exhibits active, social, and playful behavior. They are known to school in large groups in their natural habitat, which helps to provide them with a sense of security and protection from predators. They are peaceful species in the aquarium but can become territorial with other rainbowfish or similar-looking species. 


The Australian rainbowfish are best kept with other peaceful and similarly sized species. It is important to avoid keeping the Australian rainbowfish with larger or more aggressive species, as this may result in bullying or aggression towards the rainbowfish. 

Some good tankmates options for the Australian rainbowfish include:

Tank conditions

The Australian rainbowfish is a hardy species that can adapt to various water conditions. However, providing them with an aquarium as close to their natural habitat is critical. They prefer water temperatures ranging from 72 to 82 degrees Fahrenheit, pH levels ranging from 6.5 to 7.5, and water hardness ranging from moderate to high. 

It is also important to provide them with good filtration and a strong water flow, as this will help to maintain water quality and keep the aquarium clean and healthy. In terms of aquarium decor, the Australian rainbowfish enjoy plenty of hiding places and areas to explore. This can be achieved through live or artificial plants, caves, and other decorations.


The Australian rainbowfish are omnivores and enjoy a varied diet in their natural habitat. They accept various food types in the aquarium, including flakes, pellets, frozen, and live foods. Providing them with a balanced diet that includes both plant- and protein-based foods is important. 

Some good options include:

  • High-quality flakes or pellets
  • Live or frozen foods such as brine shrimp, daphnia, and bloodworms
  • Vegetables such as spinach, lettuce, and peas
  • Fresh fruits such as mango, watermelon, and cantaloupe

Avoid overfeeding the Australian rainbowfish, resulting in poor water quality and other health issues. Feeding them small portions several times a day rather than a large amount once or twice a day is best.


Breeding the Australian rainbowfish can be a rewarding experience for fish enthusiasts. Given the right conditions, these fish are relatively easy to produce in the aquarium. To encourage breeding, providing them with a spacious tank, a high-quality diet, and optimal water conditions is recommended. Additionally, it is best to keep a ratio of one male to two or three females, as this will increase the chances of successful breeding.

The Australian rainbowfish breeding process typically begins with courtship behavior, in which the male displays vibrant colors and performs specific behaviors to attract a female. If successful, the female will lay her eggs flat, and the male fertilizes them.

Once the eggs have been fertilized, the adults should be removed from the breeding tank because they may consume the eggs or fry. The eggs will hatch in 3-4 days, and the fry will be able to swim freely in another 3-4 days. They can be fed small amounts of newly hatched brine shrimp or other suitable food at this point.


The Australian rainbowfish is a hardy species but still susceptible to a few diseases. Maintaining good water quality, providing a balanced diet, and regularly monitoring the fish for any signs of illness are important.

Some common diseases that can affect the Australian rainbowfish include:

  • Ich (Ichthyophthiriasis): A parasitic disease that causes white spots on the skin and fins of the fish. This disease is often caused by poor water quality and can be treated with commercial ich medication.
  • Fin rot: A bacterial infection that causes the fins to deteriorate and the fish to become sluggish. This disease is often caused by poor water quality and can be treated with a commercial fin rot medication.
  • Swim bladder disorder: A condition that affects the fish’s ability to swim and maintain buoyancy. This condition can be caused by overfeeding or a genetic predisposition and can sometimes be treated with a change in diet.


Jason Matthews

My name is Jason Matthews, and welcome to my website. When other kids were bragging about how their dog could sit and roll over, I was bragging about my latest Betta Fish and the cool sea castle I just added to his aquarium. 

Jason aquariume

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