Aquariums, Freshwater fish, Information, Rainbowfish, Species

Neon Rainbowfish (Melanotaenia praecox)

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by Jason Matthews



The neon rainbowfish is a popular and vibrant fish species in the aquarium hobby. Its vibrant neon colors and personality make it an intriguing and appealing addition to any fish tank.

In this article, we will dive into the world of neon rainbowfish and provide an overview of everything you need to know as a beginner or intermediate fish owner, from their natural habitat and appearance to their preferred tank conditions and behavior.


Scientific Name: Melanotaenia praecox
Common Names: Dwarf neon rainbowfish, dwarf rainbowfish, diamond rainbowfish, neon rainbowfish
Life Expectancy: 3-5 years
Adult Size: 6 cm (2.4 inches)

Characteristics of Neon Rainbowfish

HabitatFreshwater rivers, streams, and lakes
OriginIndonesia and Papua New Guinea
Care LevelModerate
TemperamentPeaceful, shoaling
DietPrimarily omnivorous
Tank LevelMid to upper water level
Minimum Tank Size20 gallons (75 liters) for a small group
Water pH6.5 to 7.5
Water Temperature72°F to 82°F (22°C to 28°C)
Water HardnessSoft to slightly hard water, 5 to 12 dGH
LightingModerate to bright lighting
Tank MatesPeaceful community fish, avoid fin-nipping species

Fun Fact Corner

Did you know that neon rainbowfish can change color depending on their mood and environment? These fish are known for their stunning iridescent colors, ranging from vibrant neon greens and pinks to deep blues and purples. The color change results from the microscopic scales on their bodies, which reflect light differently based on their surroundings.


The neon rainbowfish originated in the streams and rivers of New Guinea and Indonesia. This species has a wide range and can be found in various locations, including the Indonesian islands of Biak, Numfor, and Yapen, as well as the Sepik River region of Papua New Guinea.

The neon rainbowfish is a freshwater species that live in fast-moving streams, rivers, and creeks among rocks and aquatic vegetation. These habitats provide the fish with an ideal environment that includes plenty of cover and an ample food supply.

Appearance & Size

The Neon rainbowfish body of the fish is slender and streamlined, with a slightly rounded abdomen and a pointed snout. The species is easily identified by its bright neon stripes, usually blue or green, running vertically down the body.

The neon rainbowfish is a relatively small species, with adults typically growing to a size of around 6 centimeters (2.4 inches) in length. It is important to note that the neon rainbowfish’s size can vary depending on the conditions under which it is kept.


The neon rainbowfish is a sexually dimorphic species, which means that males and females look very different. Males typically have brighter and more vivid neon stripes and longer and more elaborate fins. Females, on the other hand, are smaller, have more muted coloration, and have shorter fins.

It’s worth noting that male and female neon rainbowfish can be easily distinguished, especially once they’ve reached maturity. Males are larger and more colorful, whereas females are smaller and more subdued in appearance. However, young neon rainbowfish may not show any discernible differences, and it may take several months for them to mature and display their complete adult coloring and physical characteristics.


These fish are lively and playful, frequently swimming and jumping around their tank to show their agility and vitality. They are also social creatures that thrive in small groups of six or more people.

In the wild, neon rainbowfish live in large shoals and display high social interaction and cooperation. In the aquarium, they often form loose hierarchies, with dominant fish showing more heightened aggression towards submissive individuals. This behavior is typically short-lived and does not result in any serious harm to the fish.


Neon rainbowfish are small, peaceful fish and do best when kept with other species that are similar in size and temperament. It’s also important to consider compatibility regarding water parameters, as neon rainbowfish prefer a neutral pH and warm water temperature.

Here is a list of good tankmates option for neon rainbowfish:

Tank conditions

There are a few key factors to consider when keeping neon rainbowfish in an aquarium to ensure they thrive in their new home. The first is the quality and temperature of the water. Neon rainbowfish prefer temperatures ranging from 76 to 82 degrees Fahrenheit and a neutral pH of 7.0 to 7.8. They are also sensitive to high ammonia, nitrite, and nitrate levels, so maintaining good water quality through regular water changes and monitoring water parameters is critical.

In terms of tank size, a single neon rainbowfish requires a minimum of 20 gallons, with larger tanks needed for groups of fish. Because these fish are active swimmers who require plenty of space to swim and play, a long and narrow tank is frequently preferred over a tall and deep tank.

Regarding tank decoration and setup, neon rainbowfish thrive in aquariums that closely resemble their natural habitat in the wild. This includes a lot of vegetation, such as live or artificial plants, hiding places, driftwood, or rocks. Lighting should be bright and provide a full spectrum of light to support the health and vibrant coloration of the fish.


When feeding neon rainbowfish, providing a varied diet that includes plant and animal matter is essential. They feed on various small insects, crustaceans, and plant matter in the wild. They can be fed a diet of high-quality flake or pellet food and live or frozen foods like brine shrimp, daphnia, or bloodworms in the aquarium. 

It’s important to avoid overfeeding neon rainbowfish, as they tend to overeat and become overweight. Two to three small feedings per day are usually sufficient, and it’s a good idea to vary their diet to ensure they receive all the necessary nutrients.


Breeding neon rainbowfish can be a rewarding experience for experienced aquarists. With the right conditions, these fish will readily breed in the aquarium, providing a unique opportunity to observe the reproductive behavior and growth of the fry.

Neon rainbowfish require a large, well-planted aquarium with plenty of hiding places and a consistent water temperature to encourage breeding. A pH of around 7.0 and temperatures ranging from 75 to 82°F are ideal for breeding neon rainbowfish.

 It’s also important to provide neon rainbowfish with a varied diet that includes plant and animal matter. A high-quality protein diet will promote optimal health and encourage breeding behavior.


Several diseases can affect these fish, including bacterial infections, parasitic infestations, and fungal infections.

To help prevent disease in neon rainbowfish, maintain good water quality by performing regular water changes and monitoring water parameters. Furthermore, providing neon rainbowfish with a varied and nutritious diet and a stress-free environment will aid their overall health and resilience.

Some common signs of disease in neon rainbowfish include a loss of appetite, abnormal swimming behavior, cloudy eyes, and discolored fins or skin. If you suspect your neon rainbowfish are sick, keep them separate from the rest of the aquarium and consult a veterinarian who specializes in fish health.


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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