Rainbow shark: Epalzeorhynchos frenatum

The rainbow shark is an eye-catching aquarium fish due to its brilliant tail coloration and hardiness. It was first made explanation by American Zoologist Henry Weed Fowler in 1934. It is an appealing actinopterygian ray-finned fish which belongs to the family Cyprinidae (minnow family) of order  Cypriniformes. Synonyms of this species are Labeo frenatus Fowler, 1934, Labeo erythrura Fowler, 1937. This fish species (Epalzeorhynchos frenatum) is not threatened but it is listed as Least Concern on the IUCN Red Data List.

Systematic Position

  • Phylum: Chordata
  • Sub-phylum: Vertebrata
  • Class: Actinopterygii
  • Order: Cypriniformes
  • Family: Cyprinidae
  • Genus: Epalzeorhynchos  
  • Species: Epalzeorhynchos frenatum

Distribution and Habitat

They are distributed in South East Asian countries such as Indonesia and Thailand. It inhabits streams, rivers and inundated flooded plains. Normally, it favors living in mid and bottom areas of the water body where sandy or rocky surfaces with foods are available. They also graze for food in the forested areas during the monsoon period.

Common Names

It is also known as the Redfin Shark, Ruby Shark, Green Fringed Lip Labeo, Rainbow Shark Minnow, Whitetail Shark Minnow, Whitefin Shark and Red Finned Shark.

Body Shape

They have an elongated body with forked caudal or tail fin. The mouth is moderate with a pointed snout. It looks shark like due to upright dorsal fin and elongated streamlined body. Dorsal fin bears no spine with 10-13 branched fin rays.

Body Colors

It has dark black and greenish body but all fins are red in colors with slightly dusky black in color. A characteristic brief stripe is present in the eyes and the mouth. At the base of the caudal fin, a large dark spot is present.

Body Size and Lifespan

Its body reaches up to 22 cm long. They can survive up to 8 years if you take appropriate care.

Quick Rainbow Shark Facts

  • Scientific Name:Epalzeorhynchos frenatus
  • Origin: Thailand, Indonesia
  • Grown-up Size:  22 cm
  • Temperament: Semi-aggressive
  • Tank Level: Middle-top
  • Minimum Tank Size:  50 gallons
  • Diet: Omnivore
  • Breeding: Egg- layers
  • Water pH: 6.5 – 7.5
  • Water Temperature: 75 – 80°F (24-270C)
  • Lighting need: Normal-Moderate
  • Hardness: 8 to 12 dGH
  • Water Movement: Moderate
  • Care level: Easy
  • Lifespan:  up to 8 years

Food and Feeding Behavior

It is the omnivore and its food comprises of insect and its larvae, algae, tubifex, crustacean zooplankton such as Cyclops, Daphnia, periphyton etc. You should also offer vegetable-based food like lettuce, spinach and frozen foods like bloodworms (Chironomus larvae), or brine shrimp. Fish should be fed 2-3 times a day for keeping your fish healthy and happy.

Housing and Care Fats

50 gallons tank or larger is recommended to keep your fish happy. Lots of space with hiding spot like rocks, caves and aquarium plants (Microsorum, Bolbitis or Anubias etc) should be provided. For making suitable tank ecosystem, good water quality with sufficient oxygenated water and strong water current should be maintained. In this case, pH should be between 6.5 and 7.5 with a hardness of 8-12 dGH while water temperature that should be ranged from 75-80° F (24-27C).

This fish is an active jumper; hence the tank should be fitted with the tight-fitting lid to prevent jumping out. To keep your tank water crystal clear, you should change the partial water every other week.


They are territorial fish and you should keep it singly with other similar species. In this case, it does well with catfish, barbs, large tetras, danios, rainbowfish, plecos, loaches, rasboras, and gouramis. It should not be kept with red-tailed sharks and other rainbow sharks.

Breeding Behavior

Rainbow shark is an egg-layer and it can rarely breed in aquarium condition if you arrange appropriate care. For successful breeding, 75 gallons or larger tank with sufficient aquarium gravel is required.  When a female becomes mature, they lay eggs on the surface of the gravel in a fish tank.

Hatching occurs within 7 days after laying of eggs and fry become free swimming within a few days. The newly hatched baby fish should be fed with artemia (newly hatched brine shrimp), infusoria, and any liquid fry food.

Disease and Preventive Measures

Generally, this minnow shark is hardy and disease resistant but sometimes they are susceptible to ich or whites pot disease (a protozoans parasitic disease). To prevent disease, you should keep your tank clean and provide a balanced diet with good water quality. If you detect ich on the fish body, in this case, you should use Malachite Green solution.  As preventive measures, new fish or any decorative items such as gravel, driftwood, aquarium plants etc should be made to quarantine before adding to the fish tank. 

Male and Female Sex Differences

During the period of the juvenile, it is tough to determine male and female fish. Generally, the adult male is slimmer and their anal fin bears black lines while the females are thicker-bodied than the male. During breeding season, the mature female bears fuller belly when she carries eggs in her belly.

Also Read: Aquarium Fish Facts: Silver Arowana

Concluding Remarks

Rainbow shark is a beautiful  and attractive colored aquarium fish. It is popular among the aquarium enthusiasts due to its tail fin with brilliant body coloration. It has various color forms and they are strongly related to the Red Tailed Black Shark and now it is available in the pet fish business market. You can also purchase them easily online shops with reasonable price from home. We prescribe you to keep only one rainbow shark with other similar species in a fish tank to prevent aggressiveness. 

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