Keeping Neon Rainbowfish: Care Tips for a Vibrant and Lively Species

Dwarf neon rainbowfish (Melanotaenia praecox) is a rather popular aquarium fish kind. They are popular among aquarium enthusiasts due to their stunning appearance and active nature. It got the name due to the coloring which contains all colors of rainbow in the most unusual and unexpected combinations. Nowadays there are 72 rainbowfish kinds known. All of them inhabit in Australia and neighboring islands.

Habitat in the wild

The neon rainbowfish belongs to the family Melanotaeniidae. The family got its name due to the dark stripe (melanos – means black, taenia – stripe), which stretches along the body and it is more or less visible regardless of the kind. The family Melanotaeniidae consists of various species of rainbowfish, which are known for their vibrant colors and lively behavior. Rainbowfish are primarily found in freshwater habitats in Australia, New Guinea, and nearby islands. The family Melanotaeniidae is further divided into several genera, including Melanotaenia, Chilatherina, Glossolepis, and Rhadinocentrus, each comprising different species of rainbowfish. The neon rRainbowfish, scientifically known as Melanotaenia praecox, is one of the well-known species within the Melanotaeniidae family.

Almost every year you can see new reports about discovering more new kinds of the dwarf neon rainbowfish with unusual coloring. Natural habitats of the new kinds often intersect, however, at that there is no remote hybridization there: apparently, there must be some genetic barrier which prevents it.

This group of fishes is relatively new in aquarium husbandry. It has become famous only since 1950s, at that most of the fish kinds have become available on sale only since 80-s. The Melanotaeniidae is almost not exported from the wild, to a large extent due to successful captive breeding and difficulties when transporting the fish from outlying regions. Besides in many of these regions some of the fish kinds are threaten with extinction.

Dwarf neon rainbowfishes are native to the rivers and streams of the island of New Guinea, particularly in the regions of Papua New Guinea and West Papua. The family inhabit in the territory of Papua New Guinea, in River Mamberamo and Baliem.

Neon rainbowfish inhabit freshwater rivers and streams, often in hilly or mountainous regions. They prefer areas with moderate to fast water flow. These fish thrive in warm, tropical waters with temperatures ranging from 75°F to 82°F (24°C to 28°C). The pH level of their natural habitat typically ranges from slightly acidic to neutral, around 6.0 to 7.5. Sometimes water hardness is up to 20 dGH high, which is due to large amount of dissolved salts that ingress into the water from the soil.

Neon rainbowfish are commonly found in areas with dense vegetation, including submerged plants, floating plants, and overhanging vegetation along the banks. The presence of plants provides them with ample hiding spots and areas for foraging.


All rainbowfishes have elongated body rather flattened from sides and upward-pointing mouth with jaws having small coniform teeth. They have a slightly compressed body from the sides, which allows for swift and agile movement in the water. As the fish grows its body shape changes rather significantly. This is especially true for the male, which become more deep bodied.

The body of neon rainbowfish is predominantly a bright, iridescent blue or greenish-blue color. The intensity of the blue coloration can vary among individuals. Overall, neon rainbowfish’s combination of vibrant blue or greenish-blue body color and contrasting fins make them visually striking and highly sought after by aquarium enthusiasts.

A distinctive feature peculiar to all fishes is that they have two dorsal fins very close together. The first fin is smaller, than the second one.

Neon rainbowfish (Melanotaenia praecox) are relatively small fish, making them suitable for a variety of aquarium setups. The dwarf neon rainbowfish size reaches up to 5 cm (2.0 in) in length, but there are reports of individuals up to 8 cm (3.1 in). This measurement is from the snout to the tip of the tail fin. In terms of size, there is generally minimal difference between males and females. Both genders tend to grow to a similar length, with males occasionally having slightly longer and more elongated fins.

On average, the dwarf rainbowfish has a lifespan of around 3 to 5 years in well-maintained aquarium conditions. Providing them with a suitable environment, proper nutrition, and good water quality can help maximize their lifespan and overall health.

Scientific NameMelanotaenia praecox
Common NameNeon Rainbowfish, dwarf rainbow fish, dwarf neon rainbowfish, praecox rainbow fish
SizeUp to 2.5 inches (6.5 cm) in length
Lifespan3 to 5 years
Native HabitatRivers and streams of Papua New Guinea and West Papua
Water Temperature75°F to 82°F (24°C to 28°C)
pH Range6.0 to 7.5
Water HardnessSoft to moderately hard water
BehaviorActive, peaceful, and schooling
ColorationBrilliant blue to greenish-blue body with a red stripe
DietOmnivorous; feeds on small invertebrates and plant matter
CompatibilityPeaceful, suitable for community tanks
Tank Size20 gallons (75 liters) or larger
Tank SetupWell-planted with open swimming spaces
Water QualityClear, well-oxygenated water
BreedingEgg scatterers; breeding can be stimulated with plants
Special ConsiderationsNeon Rainbowfish prefer being kept in groups of 6 or more for better social dynamics and color display. They are jumpers, so a secure aquarium lid is recommended.

Difficulties in keeping

There are fish kinds that are easy to keep as well as rare and demanding ones. As a rule, you can encounter undemanding and adapted species on sale.

When putting dwarf neon rainbowfish into your tank you should keep in mind that the fish can jump well. When they play they often jump out of the water, so make sure that you have a proper cover for the tank.

It is recommended to buy grown up juveniles and not to look for bright colored adult species, unless it is very important for some reason. Firstly, the juveniles adapt to new conditions easier. Secondly, adult species may bring some infections into your tank together with them. Although, dwarf neon juveniles have less bright coloring, but it is more predictable. Usually, fishes are not imported, since local breeders provide them for sale. Therefore, the fish you get is not enfeebled by the transportation process and it is also adapted to the water parameters in some specific region.

Care and keeping in a tank

The fish demonstrates maximum of its coloring when it is kept in a spacious, elongated tank, which is thickly planted, but it also has some free space for the fish to swim as well.

Tank size

Melanotaenia praecox are active swimmers and benefit from having enough space to move around comfortably. While they are relatively small fish, providing them with an adequately sized tank is important for their well-being.

A general guideline for tank size for neon rainbowfish is a minimum of 20 gallons (75 liters). This size provides enough swimming space and allows for the inclusion of appropriate tank mates in a community setup. However, keep in mind that having a larger tank is always beneficial, as it provides more room for the fish to explore and reduces the chances of overcrowding.

If you plan to keep a larger group or want to include other fish species, it’s recommended to opt for a larger tank. Increasing the tank size to 30 gallons (113 liters) or more will allow for a greater number of neon rainbowfish and provide a more spacious environment for them to thrive.

Remember to consider not just the size of the tank but also its dimensions. A longer tank with ample horizontal swimming space is preferable for rainbowfish, as they are active and enjoy darting back and forth. Providing a well-planted setup with open areas for swimming and hiding spots will enhance their overall habitat.

Water parameters

In the aquarium the dwarf neon rainbowfish dwells in quite different conditions and requirements to the tank conditions vary significantly for each kind.

Optimal tank water temperature for dwarf neon rainbowfish is considered to be 75°F to 82°F (24°C to 28°C) degrees. The same is about tank water acidity and hardness which diverge greatly in various kinds of natural waters and they vary in the following range: for pH – from 6.0 to 7.5 and from 5 to 12 degrees for total water hardness.

To keep and breed dwarf neon rainbowfish in a tank there is no need for special water preparation. The only thing that matters, is the tank water quality in terms of toxic nitrogen compounds content in it. Excessive amount of the latter is not lethal for the fish, but it is highly unwanted.


Since in the wild fishes prefer fast flowing waters, it will be reasonable to create some imitation of the water flow in a tank by means of a powerful water filter or a circulating pump. As the fish prefers fresh water, it is desirable to renew ¼ of the tank water volume at least once a week (or more often).


When it comes to decorating the aquarium for neon rainbowfish (Melanotaenia praecox), it’s essential to create an environment that mimics their natural habitat while providing them with ample swimming space. Here are some decor ideas:

  1. Plants: Include a variety of live plants in the aquarium. Neon rainbowfish appreciate densely planted areas for hiding, exploring, and foraging. Opt for aquatic plants such as Java Fern, Anubias, Vallisneria, and Amazon Sword. Floating plants like Hornwort can also provide shade and cover.
  2. Driftwood and Rocks: Use driftwood pieces or rocks to create natural-looking structures and caves. These provide hiding spots and territories for the fish. Ensure the decorations are smooth and free from sharp edges to prevent any injuries.
  3. Substrate: Choose a substrate that replicates the natural riverbed environment, such as fine gravel or sand. Avoid using substrates with rough or sharp textures to protect the fish’s delicate fins.
  4. Open Swimming Areas: Create open spaces in the aquarium to allow Neon Rainbowfish to swim freely. Avoid overcrowding the tank with too many decorations, which can restrict their movement.
  5. Background: Consider adding a dark or natural-colored background to the aquarium. This can help enhance the fish’s colors and create a visually appealing backdrop.
  6. Lighting: Neon rainbowfish benefit from moderate lighting levels. Choose a lighting system that provides a natural day-night cycle, with a period of darkness to mimic their natural environment.
  7. Natural Décor Accents: To add a more natural feel, you can include dried leaves, seed pods, or branches from safe and pesticide-free sources. These can serve as additional hiding places or natural foraging spots.

Remember to arrange the decorations in a way that allows for good water flow and easy maintenance. Regularly clean the aquarium and remove any accumulated debris to maintain optimal water quality.

Tank mates

Dwarf neon rainbowfishes are rather peaceful ones. They prefer company of their kind and they are good tank mates for most of tank fishes with only one exception, which is presented by slow and long finned. They may nip their fins from time to time.

All rainbowfish kinds are schooling ones by nature and for this reason they prefer a company of their own, since there they feel much more comfortable. Therefore, it is desirable to have not less than 6 species in a group. The more fishes are in the school, the less interest they show towards other kinds. They have enough things to do within the school. The situation is quite the opposite, if there are 2-4 species in a tank.

Since the dwarf neon rainbowfish males are much brighter and slimmer than the females, it is preferable to have more male species in a group. When making efforts to attract female, the males try to show the best of them. Their coloring becomes brighter and more saturated and their movements are fast and graceful.

Rainbowfish species from the same genus, such as Melanotaenia boesemani or Melanotaenia lacustris, can make great tank mates for neon rainbowfish. They share similar water requirements and peaceful temperaments.

Here are some suitable tank mate options for neon rainbowfish:


In their native environment, neon rainbowfish are omnivorous, feeding on a variety of small invertebrates, insect larvae, algae, and plant matter. School prefers to swim in upper water layers, where the fish eagerly feeds on insects that fell into the water, which compose the main part of the diet.

Feeding is not a problem – dwarf neon rainbowfish eat all types of aquarium food, both live and artificial ones. The fish prefers taking food from the water surface or in the depth, it rather seldom feeds from the tank bottom. Optimal diet should include both live and artificial food. Dwarf neon rainbowfishes grow quite well when being fed with any type of live food too.

It is recommended to add plant food components into the diet, otherwise the dwarf neon rainbowfishes may start to damage new leaves of some tank plants. Hungry fish can nip new soft leaves of aquarium plants, though not all of the kinds do this.

You should keep in mind that rainbowfishes are rather gluttonous, that’s why you have to control the food dosage. Because the fish doesn’t know when to stop and it can easily eat non-stop and fatal outcome is quite possible in this case.

Gender differences: male vs female

Neon dwarf rainbowfish becomes reproductive at the age of 8-12 month old. As for the gender dimorphism, it begins to show from about the age of six month. The dwarf neon rainbowfish has rather pronounced dimorphism. At an early age it is quite challenging to define the gender. To avoid the situation when you have lots of unattractive female species in a tank, instead of bright colored male ones, the best option is to get the juveniles at the stage when their first signs of dimorphism start to show.

The male, as a rule, is larger and has brighter coloring than that of the female; also the body is noticeably higher, especially that of reproductive male species. When the forepart of the fish dorsal fin is folded, it reaches the beginning of the dorsal end. The edge of dorsal and anal fin ends of the female species is usually more rounded, than that of the male ones.

The color palette of most kinds of females is shifted towards gray-brown colors.

If you can’t see these signs, it’s better to get a bit larger number of the fish than it is required. Later you can leave proper number of the fish in a tank depending on their coloring.


For dwarf neon rainbowfish breeding it is enough to have a tank 50-60 cm long. The determinal factor here is only the number of breeders put for spawning into the tank simultaneously.

As for the spawning substrate, you can use several bushes of small leaved aquarium plants (Java moss) and put them along the walls or in the corner of the spawning tank. Tank water parameters don’t have any crucial significance, but it is rather preferable that the water is soft close to the neutral pH value.

The number of dwarf neon rainbowfish male species in the group of fish put for spawning should be slightly bigger, than that of the females.

It’d be rather helpful to keep the breeders separately before spawning, since this shortens the spawning time and allows obtaining the largest possible amount of eggs in 2-3 day period. Diversified diet and high feeding during this period as well as frequent renews of sufficient amount of tank water will also stimulate the spawning process.

Rainbowfishes spawn in portions. Every day during one or two weeks the female lays from 5 to 50 eggs on the plant substrate or capron threads, then there is a break that lasts for couple of weeks.

The breeding group consisting of two females and three male species can lay from 200 to 300 eggs in a week.

Eggs on the plant substrate are rather small at the beginning, but soon they will swell and grow to be up to almost 1.5 mm in diameter. Total number of the eggs is defined by the time during which the breeders stay in the spawning tank (from 2-3 to 7-8 days), their condition and number.

The eggs stick to the substrate by means of filamentary shoots. Since the breeders are capable of eating their eggs, they should be moved together with the substrate into another tank filled with water having the same parameters for further incubation.

The temperature in the incubator should be maintained constant ( ± 1°C), besides moderate aeration is also required. It is possible to add a small amount of some fungicidal agent into the water, for example, methylene blue.

Due to the size and sensitivity its embryos are quite susceptible to many kinds of organic and inorganic compounds dissolved in the water.

That’s why one of the most important conditions of successful breeding is high water quality.

Eggs of the most rainbowfishes don’t develop at daylight. For this reason, lighting in the spawning tank should be dim.

All rainbowfishes have one interesting peculiarity. Unlike other fishes, their larval stage occurs in the eggs. And when juveniles hatch from the eggs, they are already able to feed and swim actively.

Usually about 7-10 days pass from the day of laying eggs till the time when the juveniles hatch. You can keep the adult fishes in the spawning tank till the first juveniles appear. Dwarf neon rainbowfish don’t eat their eggs, but the chances are high that they may start eating the juveniles.

Newborn juveniles gather is large groups near the tank water surface, where the lighting is more intensive.

The juveniles are rather small sized. As a start food for them it’s better to use artificial food for aquarium juveniles, later it can be brine shrimp nauplii.

At that, growing the juveniles by feeding them with artificial food quite often has better results, then in case of natural microplankton diet. The thing is, that at early stages juveniles are more demanding, than grown up juveniles and adult, and they often refuse to eat at all if you give them nauplii of some other kind.

The dwarf rainbowfish neon juveniles grow unevenly, that’s why you should sort them from time to time. Otherwise, larger species may eat their smaller fellows.

For the same reason, it’s not a good idea to keep juveniles of different ages in one tank.