One look at the “rosy” glow and flashy colors of the Sepik Rainbowfish and the appeal of keeping rainbowfish speaks for itself!

The Sepik Rainbowfish Glossolepis multisquamata is yet another sparkling gem from the waterways of Indonesia. The term “multisquamata” actually means “many scales” and this rainbow fish sports a multitude of vibrant colors reflecting from those scales. The mature males develop a very distinctive and flashy coloration. Though it varies from fish to fish, they may have an overall reddish or rosy cast that will be highlighted with stripes of reflective orange, green, or blue. Another common name it is known by is the Rosy Rainbowfish.

The Sepik Rainbowfish is a strong, active, and fairly large rainbowfish, reaching about 4.8 inches (12 cm) in the aquarium. This species possesses all the qualities which make this family desirable. Besides a subtly intense beauty, their disposition is peaceful but with energy. These qualities make the Sepik Rainbowfish a perfect inhabitant for a larger tank. It can be kept with other similar sized and like tempered tank mates, but keeping a school of 6 or more of its own kind will bring out the colors in adult males. The males will entertain themselves by displaying their brightest coloration to females and posturing their rival males.

These fish are great for beginners as they are very hardy. These fish are fairly adaptable to a variety of tank conditions, but a planted tank with open swimming space suits them best. They are very active swimmers and also jumpers, so be sure the tank has a secure cover. A group of juveniles will quickly mature into a beautiful centerpiece school of active and colorful specimens. Frequent water changes are a small price to pay for this very rewarding species. This is a most excellent fish for any aquarist willing to accept the challenge.

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

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Atheriniformes
  • Family: Melanotaeniidae
  • Genus: Glossolepis
  • Species: multisquamata
Sepik Rainbowfish – Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Size of fish – inches: 5.5 inches (13.97 cm)
  • Minimum Tank Size: 30 gal (114 L)
  • Temperament: Peaceful
  • Aquarium Hardiness: Very Hardy
  • Temperature: 79.0 to 86.0° F (26.1 to 30.0&deg C)
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Habitat: Distribution / Background

The Sepik Rainbowfish Glossolepis multisquamata was described by Weber and Beaufort in 1922. It is currently found the Mamberamo river system in West Papua New Guinea. The Mamberamo River is the largest northern river of West Papua and the center of the Mamberamo river system. There are a number of tributaries, slow-flowing streams and backwaters. This species is listed on the IUCN Redlist as Least Concern (LC) because it inhabits a wide variety of relatively undisturbed habitats, but proposed developments of mining and dams, may impact its status in the future.

Another common name Glossolepis multisquamata is known by is Rosy Rainbowfish. There is some controversy over the common name “Sepik”. This species was originally collected from tributaries of the Mamberamo river system by Dutch zoologist and explorer W. C. van Heurn in 1920. However its common name “Sepik” reflects later collections from the Sepik-Ramu River region, one such collection was by ichthyologists Gerald Allen in 1979.

Further collections by Heiko Bleher, a German explorer well-known for his discoveries of many new freshwater fish species, and a number other individuals has lead to the conclusion that the specimens from the Mamberamo region are the true Glossolepis multisquamata while those from the Sepik-Ramu River system are considered to be Glossolepis kabia. Besides being from different geograhic localities, one of the most obvious difference between these two is that those from the Mamberamo region, the true Glossolepis multisquamata, have a larger anal fin.

The Sepik Rainbowfish not only inhabits lakes, small river inlets, and swampy lagoons, but is the only rainbowfish to be found in the large vegetated floodplains. They differ from many Rainbowfish as they live in more acidic waters rather than alkaline. Their habitat usually has a very slow current and typically gets a lot of sunlight. This makes their surrounding dense in plant life and algae. In nature these fish feed on invertebrates, bugs that fall into the water and plant matter.

  • Scientific Name: Glossolepis multisquamata
  • Social Grouping: Groups – Congregates in groups, like other rainbow fishes.
  • IUCN Red List: LC – Least Concern


The Sepik Rainbowfish is fully grown at 4.8 inches (12 cm). It has the typical rainbow fish shape, long but deep, with an arched back and narrow head. This fish is usually cream or silver for the base color, and is highlighted with stripes of reflective orange, green, or blue. They may also have an overall reddish or rosy cast. The exact color pattern varies from fish to fish, and there are several geographical variants. Females are usually a duller brownish coloration, with more subtle color patterns or none at all. At around 2.5 inches in length, these fish will begin to develop their beautiful characteristic colors.

  • Size of fish – inches: 5.5 inches (13.97 cm) – Usually only reaches about 4.8 inches (12 cm) in the aquarium..
  • Lifespan: 6 years – Can have a life span of 6-8 years when kept in a well maintained aquarium.

Fish Keeping Difficulty

The Sepik Rainbowfish is a fairly easy fish to keep in an aquarium. These fish are a bit easier then many of the rainbowfish to get their colors to come out. They are not as easily bothered with water condition changes as with most rainbow fish. so they make for a good beginner rainbowfish. With proper water conditions and and high quality mixes of food these fish will be a great addition to your aquarium.

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

Foods and Feeding

The Sepik Rainbowfish are omnivores that feed on invertebrates, bugs that fall into the water, and plant matter in their natural habitat. They have high nutritional requirements and need a high quality diet to promote good coloration. Provide a good mix of live and processed foods. Buy processed foods in small amounts and frequently, as the nutritional value of these products quickly deteriorates past usefulness.

The Rosy Rainbowfish enjoy and benefit nutritionally from the occasional treat of live prey. Some good live food options include bloodworms, tubifex worms, water fleas, or brine shrimp. These should be fed at least twice per week as a supplement to the prepared diet. If these are unavailable live, frozen (defrosted) substitutes would also be accepted. These fish should be fed 2 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 twice a day, 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. If a constant regimen of weekly water changes is not upheld, expect poor coloration. They are also jumpers so be sure the tank has a secure cover.

  • Water Changes: Weekly – Weekly water changes of 25 – 50%, depending on stocking density.

Aquarium Setup

The Red Rainbowfish is a fairly large and high energy rainbow fish. 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. As adults they will need a larger tank, with 50 to 60 gallons being reasonable. These fish are great jumpers, so make sure to have a secure lid on the tank. A quality canister filter will be best to maintain suitable water conditions. Powerheads should be used to create water movement through dense vegetation.

The Sepik Rainbowfish does best in a tank that is set up mimicking their natural habitat. These fish are extremely active swimmers and need open space to swim unobstructed. The tank also needs to have heavily planted areas for the fish to hide when they want too. Unlike most Rainbowfish that like more alkaline water, the Sepik prefers acidic water. Some algae growth on the tank will be a well enjoyed treat for this fish. As with most of the rainbow fish there is a need to create a fairly active current, this is not necessary with the Sepik. They do need highly oxygenated water, so some air stones will help with that.

Their natural habitat provides a lot of direct sunlight, so placing the aquarium where they can get natural sunlight will be a plus. If this isn’t possible get a high quality light that will simulate this.

  • Minimum Tank Size: 30 gal (114 L) – As adults a larger tank of 50 – 60 gallons or more is advisable.
  • Suitable for Nano Tank: No
  • Substrate Type: Sand/Gravel Mix
  • Lighting Needs: High – Strong lighting
  • Temperature: 79.0 to 86.0° F (26.1 to 30.0&deg C)
  • Range ph: 6.2-6.8
  • Hardness Range: 10 – 25 dGH
  • Brackish: No
  • Water Movement: Weak
  • Water Region: Top – Sepik Rainbowfish are active swimmers which favor the middle and upper part of the tank.

Social Behaviors

The Sepik Rainbowfish is a schooling fish which can usually socialize acceptably with other similarly sized fish. Mix them with other playful but good natured fish for best results. The geographical tank is one of the most effective and certainly aesthetically pleasing ways to showcase your rainbowfish. The aquarist may take this as far as he/she desires, whether choosing to decorate the tank to echo the rainbowfish habitat, or merely stocking it with geographically appropriate species. The rainbowfish might chase each other around a little, 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).

As schooling fish, 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 color displays if both genders are in the tank. Properly stocking rainbowfish 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
  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Yes – Groups of 6 or more are preferred.
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Monitor – Rainbowfish are active fish that can make slower fish nervous and stressed.
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Safe – Plants need to be sturdy enough to stay rooted and recover from any browsing.

Sex: Sexual differences

Sexing is difficult with young fish, but mature males will be more colorful. They have the arched back described above and will often be the more territorial sex.

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 rainbowfish 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

Most Rainbows are prone to skin flukes, parasitic infestations (protozoa, worms, etc.), ichthyobodo infection, parasitic infestations (protozoa, worms, etc.), bacterial infections (general), and bacterial disease. Goiters can be common in these fish in aquariums and normally caused from diet deficiencies, usually from not enough iodine.

Rainbowfish are generally 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 Sepik Rainbowfish is one of the rarer species of rainbowfish, when available they are usually priced a bit higher then most other rainbow fish species.