Once the beautiful Dwarf Neon Rainbowfish is established it needs no pampering!

The Dwarf Neon Rainbowfish Melanotaenia praecox is rugged and adaptable once it gets settled in the aquarium. This fish is an intelligent, beautiful and above all, a spirited fish. If kept healthy and happy these fish will always be active and amusing. They are very smart and seem to be especially aware of things going on outside the tank.

These are small rainbow fish, reaching only about 2 – 2 1/2 inches (5 – 6.35 cm), and have brilliant blue iridescent scales and brightly colored fins. Dwarf Neon Rainbowfish is just one common name. It has quite a variety of very descriptive common names as well as number of names used for developed strains. It can be found as the Neon Rainbowfish, Dwarf Rainbowfish, Peacock Rainbowfish, Praecox Rainbowfish, Diamond Rainbowfish, and the Dwarf Blue Rainbowfish just to name a few.

Dwarf Rainbowfish do not require a lot of extra care, but they are not recommended for beginners or new tanks as they don’t handle stress very well. There are few important things to keep in mind with rainbow fish. The first is that wild caught specimens often bring diseases and parasites with them. A quarantine period before adding new fish is strongly recommended. Another thing to remember is that these fish are quite active and do better in larger tanks that are fairly long. These fish are all excellent jumpers so tightly cover the tank. Clean water is important so good filtration and weekly partial water changes are essential.

Scientific Classification


Dwarf Neon Rainbowfish – Quick Aquarium Care

Aquarist Experience Level:Intermediate
Aquarium Hardiness:Moderately hardy
Minimum Tank Size:20 gal (76 L)
Size of fish – inches2.5 inches (6.35 cm)
Temperature:72.0 to 79.0° F (22.2 to 26.1&deg C)


Habitat: Distribution / Background

The Dwarf Neon Rainbowfish Melanotaenia praecox was described by Weber and Beaufort in 1922, but was first introduced in 1992. They are found in the small, lush jungle streams in Western New Guinea (formerly Irian Jaya), the Mamberamo region of West Papua.

The Dwarf Rainbowfish inhabit swift moving clear waters. These Rainbows usually live in water that stays around 75 – 82 degrees with a pH of around 6.5. These fish feed on vegetation, insects, small worms and fish eggs. Their region has not been well surveyed so the extent of their reach in that area can not be certain. There is currently insufficient data as to their status, but the Dwarf Rainbowfish were last listed in 1994 as a rare species.

  • Scientific Name: Melanotaenia praecox
  • Social Grouping: Groups – Congregates in schools.
  • IUCN Red List: DD – Data Deficient – Their region has not been well surveyed so there is insufficient data as to their status.


The Dwarf Neon Rainbowfish has most of the characteristics of the rainbowfish family, except in miniature. These fish only reach up to 2 – 2.5 inches in length.They have the long body that deepens with age, and older males usually develop the pinched in faces (look at head size compared to body size when the fish is in profile any you will see a noticeable indentation). They also have the big eyes and the twin dorsal fins of their cousins.

A few unique characteristics of the Neon Rainbow Fish include the brightly colored fins that are red on males and yellow on females. The body color is basically pinkish gray but the scales will light up in a bright blue by reflecting lighting hitting them from the front. The range of blue tones is surprising, it can be from a lavender to a teal depending on the light.

  • Size of fish – inches: 2.5 inches (6.35 cm) – This fish will reach 2 to 2 1/2 inches (5 – 6.35 cm) in length.
  • Lifespan: 4 years – Can have a life span of about 3 to 5 years when kept in a well maintained aquarium.

Fish Keeping Difficulty

The Dwarf Rainbow fish is actually a very easy fish to care for; however it is not recommended for beginners because they are so sensitive to water condition changes. Though they are small fish they still need a decent sized tank. This is because they do best in groups of 10 or more. It is advisable to keep these rainbow fish in a tank at least 20 inches long and ideally 20 or more gallons.

The Neon Rainbow fish will eat most anything offered, but will almost never eat food off the bottom. Cleaning the bottom is needed more often unless you have good tank scavenging bottom feeders. These rainbowfish are fairly easy to breed as well.

  • Aquarium Hardiness: Moderately hardy
  • Aquarist Experience Level: Intermediate

Foods and Feeding

Dwarf Neon Rainbowfish are classic omnivores, quite equally adapted to eating both animal and plant matter in the wild. In captivity they should be fed a high quality flake or pelleted food to maintain good health. Buy foods frequently and in small amounts, as the nutritional value of these products quickly deteriorates. Another large chunk of their diet should be live foods like brine shrimp, bloodworms, and tubifex worms. They also enjoy plant matter, so if you don’t have any live plants for them to nibble on, consider giving them blanched lettuce leaves or a plant based food from time to time. Feed these fish several times a day and only what they can consume in under 5 minutes.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet – They will enjoy brine shrimp, bloodworms, and tubifex worms.
  • Vegetable Food: Some of Diet – Chopped pre-soaked lettuce and peas are a great treat for these fish.
  • 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.
Dwarf Neon Rainbowfish
Image Credit: Arunee Rodloy, Shutterstock

Aquarium Care

Dwarf Neon Rainbowfish are not exceptionally difficult to care for provided their water is kept clean. These fish are sensitive to the water conditions, so need good filtration and water movement to keep them happy and healthy. A constant regimen of 25 – 50% weekly water changes is also a must. Test water conditions with every water change.

  • Water Changes: Weekly – 25-50% water change.

Aquarium Setup

Although small the Dwarf Rainbowfish are very active and likes to school in loose groups, so they need a tank at least 20 inches long and 20 gallons or more to swim in. Additionally, the tank should be securely covered as these fish are skilled jumpers and will probably do so if given the opportunity. An efficient filter and water movement is needed for the male fish to develop their coloration.

These 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. 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 by this fish.

A rainbowfish tank can be quite spectacular with the proper technique. Although these adaptable fish would certainly be happy in most conditions, the color is best displayed with a little planning. A dark substrate and backing on the tank contrasts with the colors and makes them more secure. Floating plants are a great addition to any tank, and the colors are seen well in the shadows. They also need stretches of open swimming areas. At least a third or half the tank should be open water, positioned in the middle to encourage the fish to swim there and give them a chance to show off their colors. Try, if possible, to plan for one or two hours of sunlight hitting the tank. This should be time when you can view the tank as the illumination will make the fish even more stunning.

  • Minimum Tank Size: 20 gal (76 L)
  • Suitable for Nano Tank: Yes
  • Substrate Type: Small Gravel
  • Lighting Needs: Low – subdued lighting
  • Temperature: 72.0 to 79.0° F (22.2 to 26.1&deg C)
  • Breeding Temperature: 72.0° F
  • Range ph: 6.5-8.0
  • Hardness Range: 5 – 30 dGH
  • Brackish: No
  • Water Movement: Moderate
  • Water Region: Middle – Dwarf Rainbowfish spend most of their time in the middle and upper levels of the aquarium.

Social Behaviors

The Neon Rainbowfish is basically adaptable to life in the community aquarium. They will get along best with other peaceful fish of a similar size. Remember that if you put them in a tank with big hungry fish the Dwarf Rainbowfish won’t last long.

Dwarf Rainbowfish are schooling fish and the ratio of males to females is very 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

These fish do best in groups of 10 or more. Make sure there are multiple females for each male so they do not stress the female out. These fish patrol the top to middle of the tank and can make some fish nervous because of the schooling. These fish will almost never eat off the bottom of the tank, so the need for bottom feeders is a must, also take great care not to overfeed.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Yes – Groups of 10 or more are preferred.
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Threat
    • Aggressive (): Threat
    • Safe
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Safe

Sexual differences

The male’s fins will have a red outline and the female’s fins will have a yellow or orange outline. These outlines will grow more distinct as the fish ages. Females are also more silver in color.

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 females have produced eggs, the males will display and direct the female to the spawning site, spawn, and then rest. They will repeat this daily for a few days, with steadily decreasing numbers of eggs produced. The parents should be removed when eggs numbers fall or if the females show signs of fatigue. The fry will hatch after a few days and should be fed infusoria or a liquid fry food until they are able to eat microworms or baby brine shrimp. The fry are something of a challenge to raise until they are about two months old.

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 Dwarf Neon Rainbowfish is also sold as the Praecox Rainbowfish, Neon Rainbowfish, Peacock Rainbowfish, Dwarf Blue Rainbowfish, Diamond Rainbowfish, and a number of other names for specific strains. It is widely available in pet stores and online and is usually moderate priced.



 Dwarf neon rainbows (Image Credit: Anandarajkumar, Wikimedia Commons CC BY-SA 3.0 Unported)