What to Know About Rainbow Shark

Reviewed by Vanesa Farmer, DVM on January 05, 2023

The aquatic world is full of a variety of species called sharks. Most people are familiar with the large, oceanic predators that you can find in waters throughout the world. But fewer people are aware of their very distant relatives — a type of bony fish called the rainbow shark.

Unlike their larger counterparts, rainbow sharks are actually small freshwater fish that are perfect for many home aquariums. But — as their shark name implies — these fish have some aggressive tendencies. They’re not recommended for beginners. Make sure to thoroughly do your research before you decide to bring one of these unique creatures home with you.

What Is a Rainbow Shark? 

Rainbow sharks are not true sharks. True sharks are in the biological order Chondrichthyes — which contains cartilaginous fishes. Rainbow sharks are in the Actinopterygii order — which contains bony, ray-finned fishes. The scientific name for the rainbow shark is Epalzeorhynchos frenatus.

These creatures also go by many different common names including the: 

  • Ruby shark 
  • Red-fin shark
  • Red-finned shark
  • Rainbow sharkminnow
  • Green fringelip labeo
  • Whitefin shark
  • Whitetail sharkminnow

Where Can You Find Rainbow Sharks?

Rainbow sharks are native to water basins in the regions between China and Indonesia. They prefer to live on sandy river bottoms. During the rainy season, these rivers swell and their territory temporarily expands into the flood zones.

Researchers are currently investigating ways to get them to reproduce in aquarium settings. But so far most rainbow sharks in the aquarium trade come from large-scale fish farms in Southeast Asia.

Physical Characteristics of Rainbow Shark

Rainbow sharks have long, elongated bodies and pointed snouts. The maximum rainbow shark size is about six inches long. 

Their bodies can come in a variety of colors, including:

  • Greenish brown
  • Black
  • Dark blue
  • Bright blue 

They also have a distinct black spot just before their tail fins. Their fins range from red to orange in color with some dusky black regions.

The males tend to be more brightly colored than the females. The males also have multiple black stripes on their tailfins and a thinner body pattern. These physical differences between the sexes are called sexual dimorphisms. 

There are three main rainbow shark variants in the aquarium trade: 

  • Albinos. This variant was created randomly in nature. They have white bodies and red-orange fins. Otherwise, they are just like normal rainbow sharks in terms of body shape and temperament. 
  • Ghost sharks. This is a much rarer variant that can be difficult to find at pet stores. Its body is identical to the typical rainbow shark except that its fins are a translucent white color instead of red or orange. 
  • Galactic purple rainbow sharks. This is a man-made variant of the rainbow shark. It’s part of the commercial GloFish series. These fish have been genetically modified to glow under ultraviolet light. Their bodies produce fluorescent light in a properly-lit tank. GloFish can be modified in different ways to produce a variety of colors. In this case, the fish are designed to produce a purple luminescence.

The exact rainbow shark lifespan depends on the quality of its care, but owners report the average is about four to six years in captivity. Some sources say that they can live for up to five to eight years.

Are Rainbow Sharks Aggressive? 

As their name implies, rainbow sharks have more aggressive personalities than many other ray-finned fishes. They’re considered a semi-aggressive breed in aquarium environments. Luckily, they’re too small to be any kind of threat to their owners. 

However, if they’re kept in a tank that’s too small they’ll harass and bully other fish. They’ll also increase the chances of your fish jumping out of the tank. Even in a correctly sized tank, they’ll continue to harass fish that are small and weak. 

In the wild, rainbow sharks exist in harmony with other members of their kind. But you should never keep them together in the same tank. They’ll constantly fight and produce threat displays. Larger ones will chase smaller ones until they die — or at least until they completely clear out of their territory. 

To minimize these risks, you need to maintain an ideal aquarium environment — complete with lots of plants and artificial places to hide. You should also carefully select the other fish that you put in the same tank as your rainbow shark. You can find a list of appropriate species in the basic care section.

What Do Rainbow Sharks Eat? 

In the wild, Rainbow sharks are mostly herbivores — which means that they only eat plants. In their natural habitats, they survive off of: 

  • Algae
  • Periphyton
  • Phytoplankton
  • Certain zooplankton

But they also become omnivorous when their environment requires it. In aquarium set-ups they will eat left-over fish food and the algae off of the bottom and sides of your tank. You can also give them algae pellets, flakes, or tablets. 

If provided, rainbow sharks will also consume: 

  • Live insects
  • Live insect larvae
  • Frozen bloodworms
  • Frozen brine shrimp
  • Lettuce
  • Spinach

Basics of Rainbow Shark Care

Due to their semi-aggressive nature, rainbow sharks should only be kept with particular species of fish. This includes: 

  • Barbs
  • Rainbowfish
  • Danios
  • Roaches
  • Plecos
  • Rasboras
  • Gouramis

When they’re kept with other species, they’ll constantly try to fight them — creating disruption and death throughout your aquarium. You shouldn’t keep them with: 

  • Any small, timid species of fish
  • Other rainbow sharks
  • Red-tailed sharks
  • Bala sharks
  • Black sharks

Rainbowfish need a tank that’s a minimum of 55 gallons and 48 inches long. Your tank conditions should also include: 

  • A temperature that’s between 75 degrees Fahrenheit and 81 degrees Fahrenheit
  • A neutral pH — between 6 and 8
  • A water hardness that’s between 5 and 11 dH
  • A sandy substrate
  • Plenty of real or fake plants 
  • Artificial hiding places — like rock caves or artificial tunnels

The temperature of your tank is particularly important. This species cannot survive at low water temperatures. Rainbow sharks that are flushed or manage to escape into the environment likely won’t survive in many non-native waterways. Fortunately, this means that they’re less likely to become invasive pests than other species in their biological order.

Rainbow Shark Health Issues

All pet fish are at risk of developing health issues throughout their lives. This includes problems like bacterial infections. 

If you believe that your fish is sick, you can try finding a veterinarian that is knowledgeable about aquarium pets. Otherwise, you can try looking for experts online and at local pet stores. 

For the right owner, rainbow sharks are fantastic aquatic pets. They can even help keep your tank clean. But these semi-aggressive creatures can cause problems for beginners. Make sure that you’re prepared to handle this unique species before introducing them to your home aquarium.

Show Sources

Canadian Journal of Zoology: “Cold temperature tolerance of albino rainbow shark (Epalzeorhynchos frenatum), a tropical fish with transgenic application in the ornamental aquarium trade.”
Encyclopedia of Life: “Rainbow Shark.” 
Fishbase: “Epalzeorhynchos frenatum (Fowler, 1934).” 
Fishkeeping World: “Rainbow Shark Care Guide & Species Profile.”
North American Journal of Aquaculture: “Induced Spawning of Rainbow Sharks (Labeo erythrurus) and Redtail Black Sharks (L. bicolor).” 
University College London: “Actinopterygii - ray-finned fishes.” 
Zebrafish: “Learning the scientific method using GloFish.” 
Aquarium Source: "Rainbow Shark 101: Care Guide, Tank Size, Food & Tank Mates

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