Rainbow Shark Care Guide

rainbow shark


Rainbow Sharks, also known as Red-Finned Sharks, are a popular freshwater fish species in the aquarium hobby. These fish are native to Thailand and Indonesia, and are a member of the Cyprinidae family. One of the unique features of the Rainbow Shark is its dark black body with bright red fins, which can make it resemble a shark to the untrained eye.

Rainbow Sharks are known for their territorial behavior and semi-aggressive temperament, which can make them challenging to keep with certain tankmates. However, when provided with adequate space and hiding places, they can make a stunning addition to a community aquarium. In this guide, we’ll explore the key characteristics of the Rainbow Shark, as well as the best practices for keeping them healthy and happy in a home aquarium.

Summary Table

Common NameRainbow Shark
Scientific NameEpalzeorhynchos frenatum
Origin / DistributionThailand and Indonesia
Size6 inches (15 cm)
Aquarium Size55 gallons (208 liters) or larger
Water ParametersTemperature: 75-81°F (24-27°C), pH: 6.5-7.5, Hardness: 5-12 dGH
DietOmnivore, primarily herbivorous
Feeding FrequencyOnce or twice daily
TemperamentTerritorial and semi-aggressive
TankmatesAvoid small or slow-moving fish, can be kept with other semi-aggressive species
BreedingBreeding is difficult in captivity
Lifespan5-8 years
Care LevelIntermediate
Unique Features / AppearanceDark black body with bright red fins, sometimes mistaken for a shark due to its appearance
Conservation StatusLeast Concern (LC)
Additional NotesCan be sensitive to water quality, provide hiding places and plenty of swimming space for optimal health.


Rainbow Sharks belong to the following taxonomic classification:

  • Common Name: Rainbow Shark or Red-Finned Shark
  • Scientific Name: Epalzeorhynchos frenatum
  • Family: Cyprinidae
  • Order: Cypriniformes

Cyprinidae is a diverse family of freshwater fish that includes over 3,000 species, making it one of the largest fish families in the world. Many popular aquarium fish species, such as goldfish and koi, belong to this family. The order Cypriniformes includes a wide range of freshwater fish species, including minnows, carp, and loaches. Rainbow Sharks are a popular and distinctive member of this diverse group of fish.

Natural Habitat & Distribution

Rainbow Sharks are native to Southeast Asia, specifically Thailand and Indonesia. They are primarily found in rivers and streams with fast-moving water and rocky bottoms. In the wild, they are often found in areas with dense vegetation and rock formations, which provide hiding places and shelter from the strong currents.

These fish have also been introduced to other regions, such as Hawaii and parts of the United States, where they are considered an invasive species. In their natural habitat, Rainbow Sharks play an important role in the ecosystem as bottom-feeders, helping to clean up debris and algae. In the aquarium, they can be a valuable addition to a community tank, as they help to maintain a healthy and balanced environment.

Physical Appearance

Rainbow Sharks are a striking and distinctive fish species that are instantly recognizable by their dark black bodies and bright red fins. These fish have a streamlined body shape and can grow up to 6 inches (15 cm) in length. Adult Rainbow Sharks can weigh up to 1.5 ounces (42 grams).

The body of the Rainbow Shark is long and slender, with a slightly curved dorsal fin and pointed pectoral fins. The tail fin is forked and has a distinctive black and white coloration. The body is typically black or dark gray, while the fins are bright red, creating a bold contrast that makes this fish a standout in any aquarium.

There is little sexual dimorphism in Rainbow Sharks, meaning that males and females are difficult to tell apart based on their physical appearance alone. However, during breeding season, males may develop more vibrant coloration and may exhibit more aggressive behavior than females.

Behavior & Temperament

Rainbow Sharks are known for their territorial behavior and can be semi-aggressive towards other fish in the aquarium. In the wild, these fish are solitary and territorial, and they will defend their preferred hiding places and feeding areas from other fish. In the aquarium, Rainbow Sharks may exhibit similar behavior, and they may become aggressive towards other bottom-dwelling fish or fish with similar body shapes.

However, Rainbow Sharks can also be kept with other semi-aggressive species, as long as they are provided with enough space and hiding places to establish their own territories. When kept in a suitable environment, Rainbow Sharks can be peaceful and fascinating to observe.

In general, Rainbow Sharks are not schooling fish, and they are most comfortable when kept alone or in pairs. They are active swimmers and require ample swimming space to remain healthy and happy.

Suitable tankmates for Rainbow Sharks include larger, non-aggressive species that occupy different areas of the aquarium. Some examples of compatible tankmates include angelfish, barbs, and gouramis. It is best to avoid small or slow-moving fish, as well as fish with similar body shapes or coloration.

Aquarium Requirements

Rainbow Sharks require a spacious and well-maintained aquarium to thrive in captivity. Here are the key requirements to keep in mind when setting up an aquarium for Rainbow Sharks:

Minimum tank size

A minimum tank size of 55 gallons (208 liters) is recommended for a single Rainbow Shark. Larger tanks are recommended for multiple fish or for providing more swimming space.

Water parameters

Rainbow Sharks prefer water temperatures between 75-81°F (24-27°C), a pH range of 6.5-7.5, and a hardness level of 5-12 dGH. It is important to maintain stable and consistent water conditions to keep these fish healthy.

Filtration and aeration

Rainbow Sharks require a good filtration system to maintain water quality, as well as adequate aeration to provide oxygenation for the fish.

Substrate preferences

These fish prefer a substrate that is fine-grained and does not have sharp edges, as their bellies are sensitive and can be easily damaged.

Lighting requirements

Rainbow Sharks do not have specific lighting requirements, but a regular lighting schedule can help to regulate their behavior and maintain a consistent day-night cycle.

Decorations and hiding places

Rainbow Sharks require plenty of hiding places in their aquarium, such as rocks, driftwood, and plants. These fish are known for their territorial behavior, and providing ample hiding places can help to reduce aggression towards other fish in the aquarium.

Diet & Feeding

Rainbow Sharks are omnivores, but they are primarily herbivorous and require a diet that is high in plant matter. Here are the key considerations for feeding Rainbow Sharks in the aquarium:

Type of diet

Rainbow Sharks require a balanced and varied diet that includes high-quality commercial fish food, such as pellets or flakes, as well as fresh or frozen vegetables, such as zucchini or spinach. They may also enjoy occasional treats, such as brine shrimp or bloodworms.

Feeding frequency

Rainbow Sharks should be fed once or twice daily, depending on their age and size. It is important not to overfeed these fish, as they are susceptible to obesity and other health issues.

Tips for providing a balanced and varied diet

To ensure that your Rainbow Sharks are receiving a balanced and varied diet, it is important to offer a mix of commercial fish food and fresh or frozen vegetables. Some suitable vegetables for Rainbow Sharks include zucchini, spinach, and peas. It is also a good idea to vary the type of fish food you offer, such as alternating between pellets and flakes, or offering different types of treats occasionally.

Tank Mates

Rainbow Sharks can be semi-aggressive and territorial towards other fish in the aquarium, so it is important to choose compatible tankmates carefully. Here are some key considerations for selecting tankmates for Rainbow Sharks:

Compatible species

Rainbow Sharks can be kept with larger, non-aggressive fish species that occupy different areas of the aquarium. Some suitable tankmates for Rainbow Sharks include angelfish, barbs, gouramis, and larger tetras.

Incompatible or potentially problematic species

Rainbow Sharks should be kept away from small or slow-moving fish, as well as fish with similar body shapes or coloration. They may also become aggressive towards other bottom-dwelling fish or fish with similar behavior, such as other semi-aggressive species.

Recommendations for creating a harmonious community tank

To create a harmonious community tank with Rainbow Sharks, it is important to provide ample swimming space and hiding places for each fish. This can help to reduce aggression and territorial behavior. It is also important to maintain stable water conditions and avoid overstocking the aquarium, which can lead to stress and aggression among the fish.


Breeding Rainbow Sharks in captivity can be difficult, and it is not a common occurrence in the aquarium hobby. Here are some key considerations for breeding Rainbow Sharks:

Breeding behavior

Rainbow Sharks are egg-layers and exhibit little to no parental care for their young. During breeding season, males may exhibit more aggressive behavior and may chase females around the aquarium.

Ideal breeding conditions

To encourage breeding, it is important to provide optimal water conditions, including stable water temperature, pH, and hardness levels. It is also recommended to provide ample hiding places for the fish, such as caves or dense vegetation.

Raising fry (offspring) and specific care requirements

Rainbow Shark fry can be difficult to raise in captivity, as they require specific water conditions and care. The fry should be kept in a separate tank with clean and well-oxygenated water, and fed a diet of freshly hatched brine shrimp or other suitable food. It is also important to monitor water quality and maintain stable water conditions for the fry to thrive.

Health & Disease

Like all fish, Rainbow Sharks are susceptible to a variety of health issues and diseases. Here are some common diseases and their symptoms, as well as prevention and treatment strategies:

Common diseases and their symptoms

Rainbow Sharks may be prone to various diseases, including bacterial infections, parasitic infections, and fungal infections. Symptoms of these diseases can include lethargy, loss of appetite, abnormal swimming behavior, and visible signs of physical damage or discoloration.

Prevention and treatment strategies

To prevent disease in Rainbow Sharks, it is important to maintain stable and consistent water conditions, including water temperature, pH, and hardness levels. Providing a balanced and varied diet can also help to support the fish’s immune system and overall health. If your Rainbow Shark shows signs of illness, it is important to isolate the fish in a separate tank and seek advice from a veterinarian or experienced aquarium hobbyist. Treatment strategies may include medication, water changes, and other measures to improve water quality and reduce stress on the fish.

Care Level

Rainbow Sharks require a moderate to advanced level of care in the aquarium. Here are some key considerations for caring for Rainbow Sharks:

Difficulty of care

Rainbow Sharks are not recommended for beginner aquarium hobbyists, as they require a well-maintained and spacious aquarium with stable water conditions and plenty of hiding places. These fish can also be semi-aggressive and territorial, so careful consideration should be given to selecting suitable tankmates.

Special considerations or requirements

Rainbow Sharks require a balanced and varied diet that is high in plant matter, as well as ample swimming space and hiding places in the aquarium. They may also be prone to disease or health issues, so careful monitoring of water quality and fish behavior is essential. Breeding Rainbow Sharks in captivity can be difficult and may require specialized equipment and expertise.

Conservation Status

Rainbow Sharks are not currently classified as a threatened species, and they are not listed on the IUCN Red List. However, like all wild animals, Rainbow Sharks face threats from habitat loss and degradation, overfishing, and other human activities.

In some regions, Rainbow Sharks are considered an invasive species and may be subject to legal restrictions on their import, sale, or possession in captivity. It is important to research local laws and regulations before acquiring Rainbow Sharks for your aquarium.

As with all fish species, it is important to ensure that Rainbow Sharks available in the aquarium trade are sustainably sourced and ethically traded. By choosing reputable and responsible aquarium retailers, you can help to support conservation efforts and promote sustainable practices in the aquarium hobby.

Additional Information & Fun Facts

  • Rainbow Sharks are not actually sharks, despite their name. They are a type of freshwater fish in the Cyprinidae family.
  • Rainbow Sharks are also known by other common names, including Red-Finned Shark, Red-Fin Shark Minnow, and Ruby Shark.
  • In the wild, Rainbow Sharks inhabit rivers and streams in Southeast Asia, including Thailand and Malaysia.
  • Rainbow Sharks are popular in the aquarium trade for their striking coloration and unique appearance. They are sometimes kept in planted aquariums, where they can help to control algae growth.
  • Despite their semi-aggressive behavior, Rainbow Sharks can develop close bonds with their owners and may even follow them around the aquarium.
  • Some hobbyists have reported that Rainbow Sharks can be trained to recognize their owners and respond to their presence by swimming to the front of the tank or performing other behaviors.
  • Rainbow Sharks have a lifespan of around 5-8 years in captivity, but they can live longer with proper care and nutrition.

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