rainbow shark feature

Essential Guide to Caring for Your Rainbow Shark

Rainbow sharks, also known as Epalzeorhynchos frenatum, are one of the most captivating species in the world of aquatics. Their fiery-red fins and dark, sleek bodies make them the envy of the aquarium. Native to Thailand, these freshwater swimmers are known for their solitary, territorial nature.

Despite their aggressive disposition, with the right care and environment, they can make a fascinating addition to a home aquarium.

rainbow shark

What Are Rainbow Sharks?

Rainbow Sharks, or Epalzeorhynchos frenatum, aren’t true sharks but a species of tropical carp. Their alternative names, Red-finned or Ruby Sharks, reflect their strikingly vibrant red or ruby-coloured fins that contrast with their dark bodies.

While they aren’t inherently aggressive, they are notoriously territorial, particularly with their own kind. Uniquely, they prefer to dwell and explore at the bottom of their habitat, favouring areas with plenty of hiding spots like caves and plants. In short, Rainbow Sharks combine captivating aesthetics with fascinating behavioural traits, offering a truly distinctive addition to any aquarium.

Rainbow Shark Facts & Overview

Rainbow Shark FactDetails
Scientific Name:Epalzeorhynchos frenatum
Care Level:Moderate
Native Region:Southeast Asia
Lifespan:5–8 years, up to 10 years in optimal conditions
Size:Up to 6 inches (approximately 15 cm)
Minimum Tank Size:200+ litres (55 gallons)
Compatibility:Compatible with a variety of active, similarly-sized species


Rainbow Sharks are native to the freshwaters of Southeast Asia, primarily originating from Thailand. They inhabit the warm, tropical rivers and streams where they relish the diverse underwater environment, often seen navigating the bottom regions in search of food.

Over time, they’ve been bred extensively for the aquarium trade due to their appearance and behaviour. While their wild population isn’t thoroughly studied, their habitat is unfortunately threatened by pollution and human development. This serve as a vibrant reminder of the extraordinary biodiversity found in these waters, and the need to protect such habitats.

Understanding the Appearance and Behaviour of Rainbow Sharks

General Appearance

  • Body: These fish possess a streamlined, elongated body, similar to that of a shark, showcasing a vibrant dark, often black, body that may sometimes exhibit a greenish hue.
  • Fins: The bright red or ruby fins, including the caudal, dorsal, pectoral, and anal fins, provide a stunning contrast to their dark body, becoming their most distinguishing feature.
  • Other Features: They have a pointed snout and a pair of barbels near their mouth, which assist them in scavenging food from the bottom of their habitat.
albino rainbow shark

The Albino Rainbow Shark

The Albino Rainbow Shark sometimes called albino ruby shark, is a variant of the standard Rainbow Shark. Just as its name suggests, this variant exhibits albinism, which is a condition characterised by a lack of pigmentation. The Albino Rainbow Shark possesses a pale, pinkish-white body, creating a stark contrast to the dark hue of the traditional Rainbow Shark.

Despite their paler body, they retain the distinctive red or pink fins of their non-albino counterparts. This combination of pale body and vibrant fins makes the Albino Rainbow Shark a truly distinctive and attractive addition to an aquarium.

They are cared for in the same way and possess the same temperament as the standard rainbow shark

Rainbow Shark Male or Female

Mature males tend to be slimmer and slightly smaller than females. The black line running along the edges of the male’s anal fin is often more intense than that of the female. Additionally, females may have a more rounded abdomen, especially during breeding season. However, these differences are subtle and may not be apparent in all individuals.

rainbow shark bottom dwelling

General Behaviour and Temperament

Typical Behaviour Rainbow Sharks are known for their active, bottom-dwelling nature. They are often seen swimming along the bottom of their tanks, exploring their surroundings and searching for food. They also enjoy having plenty of hiding spaces like caves or dense plantations, where they retreat when they feel threatened or stressed. Moreover, they are also nocturnal, meaning they’re more active during the night and prefer to rest or hide during the day.

Are Rainbow Sharks Aggressive? They are considered a semi-aggressive fish. Especially towards their own kind and other bottom-dwelling fish, particularly in a confined space. This is due to their territorial nature. They often claim a certain part of the aquarium as their own and guard it against intruders.

This territoriality can lead to chasing or nipping, especially if the tank is too small or lacks enough hiding spaces. Therefore, they are not recommended for small or crowded aquariums or with timid or slow-moving species that can’t evade their advances.

Rainbow Shark Lifespan & Size

  • Rainbow Shark Size: Rainbow Sharks generally reach an adult size of about 6 inches (15 cm).
  • Lifespan: On average, they can live between 5 and 8 years. However, in optimal conditions, they can live up to 10 years or more.

Habitat and Tank Requirements

Rainbow Shark Tank Size

As a guideline, the minimum tank size for a single Rainbow Shark should be 200+ litres or 55 gallons. This size allows enough room for the fish to move freely, reducing territorial disputes and stress.

However, if you’re planning to introduce other fish into the aquarium, particularly other bottom-dwelling species, you should consider a larger tank. For each additional Rainbow Shark or similar sized fish, add an extra 40 gallons to the tank size. This will ensure all fish have adequate territory and reduce the chance of aggressive behaviour.

Rainbow Shark Water Parameters

Maintaining the correct water parameters is crucial for the health and wellbeing of your Rainbow Shark. Here are the ideal conditions you should aim for:

  • Temperature: Rainbow Sharks thrive in tropical temperatures. The water temperature in the tank should be kept between 22°C to 26°C (72°F to 80°F).
  • pH: They prefer slightly acidic to neutral water conditions. The ideal pH range is between 6.5 and 7.5.
  • Hardness: It’s generally recommended to keep the water hardness between 5 and 15 dH.
  • Water Cleanliness: Regular water changes are a must to maintain cleanliness. It’s crucial to keep the nitrate levels low, as high levels can cause stress and illness.

Please note that abrupt changes in these parameters can be very harmful to Rainbow Sharks, so changes should always be made gradually. rainbow shark in undergrowth

Habitat and Requirements

  • Substrate: Rainbow Sharks prefer fine gravel or sand as a substrate, which allows them to root around and forage for food as they would in their natural habitat.
  • Lighting: Moderate lighting is ideal. Too bright lighting may cause stress.
  • Filtration: Good filtration is necessary to maintain water quality. A powerful filter that can handle the bioload and create a moderate current is recommended, as Rainbow Sharks are used to flowing waters in their natural habitat.
  • Heater: A reliable aquarium heater is essential to maintain the water temperature within the ideal range.

Décor and Ideal Plants


  • Caves and Rocks: Caves made from rocks or aquarium-safe materials can provide Rainbow Sharks with a private space. You can create arches or small alcoves using rocks.
  • Driftwood: Pieces of driftwood not only add a natural look to your tank but also serve as additional hiding spots.

Ideal Plants:

  • Java Fern: This plant is hardy and easy to care for. Its wide leaves provide excellent cover
  • Anubias: Another robust plant that can thrive in various conditions. Anubias has broad leaves, providing great hiding spots.
  • Amazon Sword: With its tall, broad leaves, this plant offers excellent cover and contributes to a natural-looking aquarium.
  • Cryptocoryne: Available in various species and sizes, these plants are perfect for creating a diverse and interesting landscape.
  • Java Moss: This is a great plant for covering rocks and driftwood, creating additional hiding spots and enhancing the tank’s natural look.

When adding plants, ensure they are well-rooted or tied down, as Rainbow Sharks can dislodge poorly secured plants while exploring or foraging. Remember, an aquarium that closely mimics a Rainbow Shark’s natural habitat helps promote healthy and natural behaviour.

rainbow shark feeding

Rainbow Shark Care

Rainbow Shark Diet & Feeding

Rainbow Sharks are omnivores, meaning they eat both plant matter and animal-based foods. Here’s what their diet can include:

  • Commercial Foods: High-quality pellets or flakes designed for omnivorous fish can make up the bulk of their diet. These usually contain a balanced blend of proteins, vegetables, vitamins, and minerals.
  • Live or Frozen Foods: Supplement their diet with live or frozen foods like brine shrimp, daphnia, and bloodworms. These not only provide essential proteins but also stimulate the Rainbow Shark’s natural hunting instincts.
  • Vegetables: Occasionally, offer blanched vegetables such as peas, spinach, or zucchini. These can contribute beneficial fibres and nutrients to their diet.
  • Algae and Plant Matter: Rainbow Sharks also graze on algae and soft plant matter in the tank, which can contribute to their intake of vegetable matter.

Remember to feed them in small quantities 1-2 times a day, offering only as much food as they can consume in a few minutes. Overfeeding can lead to health issues and pollute the tank. Maintain a varied diet to ensure they receive all the necessary nutrients.

Health and Diseases

Rainbow Sharks, like all fish, are prone to certain health issues and diseases. However, providing excellent care and maintaining a clean, stress-free environment can help mitigate many potential problems.

  • Ich (White Spot Disease): This is a prevalent parasitic disease where fish develop white spots on their bodies and fins. Symptoms include scratching against objects, erratic swimming, and loss of appetite. Treatment usually involves over-the-counter medication and a slight increase in the tank temperature to expedite the parasite’s lifecycle.
  • Swim Bladder Disease: This condition impairs a fish’s ability to maintain its buoyancy. Indications include swimming upside-down, floating, or sinking. Various factors can cause it, from poor diet to bacterial infections, and treatment can involve dietary adjustments or specific medications.
  • Fin Rot: A bacterial disease that causes the fins to fray or rot away. It typically occurs in poor water conditions or if a fish is stressed. The best treatment is improving water conditions and potentially using antibiotic treatments.
  • Fungal Infections: These appear as fluffy white growths on the skin and can occur due to stress, injuries, or poor water quality. Treatment involves anti-fungal medications.
  • External Parasites: These include flukes, lice, or anchor worms. Symptoms are similar to ich, and treatment involves specific anti-parasitic medications.
  • Stress-Related Issues: RainBow Sharks can suffer from Stress-Related Issues due to their territorial nature and active lifestyle. For instance, if their environment is too small, lacks hiding spaces, or if they’re housed with incompatible tank mates, they can become stressed, which could lead to a weakened immune system and increased susceptibility to various diseases.
rainbow shark tank mates

Rainbow Shark Tank Mates

Choosing suitable tank mates for Rainbow Sharks is essential due to their semi-aggressive and territorial nature. They do best with species that match their size, activity level, and temperament. Here are some ideal tank mates:

  • Barbs: Active and fast swimmers like Tiger Barbs or Rosy Barbs can hold their own with Rainbow Sharks.
  • Danios: Fast, active species like Zebra Danios or Pearl Danios are good matches.
  • Rainbowfish: Their similar size and active nature make them suitable companions.
  • Gouramis: Larger Gouramis can hold their own, but avoid smaller or more timid species.
  • Loaches: Species such as Clown Loaches or Yoyo Loaches, which also prefer bottom dwelling, can coexist with Rainbow Sharks.
  • Angelfish: Larger Angelfish might be able to coexist with Rainbow Sharks, but their slow-moving and peaceful nature could make them targets for the shark’s territorial behaviour.
  • Cichlids: Some types of larger, more aggressive Cichlids may work, but smaller, less aggressive Cichlids could become targets.

Tank Mates to Avoid

Certain species are typically not suitable due to their size, temperament, or habitat preferences:

  • Betta Fish, Goldfish, Guppies, Neon Tetras: These species are generally not recommended as they are slow-moving, peaceful, or small fish that may be bullied by the Rainbow Shark.
  • Turtles, Crabs, Shrimp: These are generally not suitable tank mates. Turtles can be dangerous to fish, while crabs and shrimp may become a meal for the Rainbow Shark due to their small size and bottom-dwelling habits.
  • Other Rainbow Sharks: Despite their beauty, housing multiple Rainbow Sharks together is typically not recommended due to their highly territorial nature. They may engage in continuous aggressive behaviour, leading to high stress levels and potential injury. If you wish to keep more than one Rainbow Shark, ensure the tank is exceptionally large with numerous hiding spots to delineate territories.

Remember, it’s generally advised to keep only one Rainbow Shark per tank, unless it’s particularly large with plenty of hiding spots. Always closely monitor any new additions for signs of aggression or distress. Each Rainbow Shark has a unique personality, and what works for one might not work for another. Always monitor new additions closely to ensure compatibility.

Can you Breed Rainbow Sharks

Breeding Rainbow Sharks in a home aquarium is extremely difficult and is rarely successful. Unlike many other fish species, Rainbow Sharks do not have well-documented breeding habits and do not readily reproduce in captivity.

Most of the Rainbow Sharks available in the pet trade are bred commercially on fish farms, often using hormonal methods to induce spawning. If you’re an amateur aquarist, it’s unlikely you’ll be able to breed these fish successfully. As such, breeding Rainbow Sharks should generally be left to professionals or highly experienced hobbyists.

rainbow shark and bala shark

Inter-species Comparisons

Rainbow Shark vs Bala Shark and Red Tail Shark

  • Bala Shark: Bala Sharks can grow much larger than Rainbow Sharks, up to 14 inches (35 cm) in length, and they require significantly larger tanks as a result — a minimum of 150 gallons (570 litres) is recommended. They have silver bodies with black margins on their fins. Bala Sharks are schooling fish and are generally more peaceful than Rainbow Sharks. They do best in groups of five or more and need plenty of open swimming space.
  • Red Tail Shark: Red Tail Sharks have a similar body shape and size to Rainbow Sharks but are entirely black except for their vibrant red tail. They also exhibit a high degree of territoriality, comparable to the Rainbow Shark, and can be quite aggressive, especially in confined spaces.

When considering either of these species for your aquarium, it’s essential to account for their territorial nature and need for space. Housing them together or with other bottom-dwelling fish often results in conflict. They’re best suited to a spacious tank with plenty of hiding spots and fast-swimming tank mates that inhabit the upper levels of the tank.

Should You Get a Rainbow Shark for Your Aquarium?

The decision to get a Rainbow Shark for your aquarium comes with its own set of benefits and drawbacks.


  • Visual Appeal: The Rainbow Shark’s dark body contrasted by its vivid red fins makes it a visually striking addition to any aquarium.
  • Active Swimmers: Their active nature and unique bottom-dwelling behaviour can be fascinating to observe.
  • Hardy Species: Rainbow Sharks are relatively hardy once acclimated, making them resilient against changes in water parameters.


  • Territorial Behaviour: Their aggressive territorial behaviour can cause stress and conflict, particularly in smaller tanks or with certain tank mates.
  • Tank Size: They require a larger tank (minimum of 125 litres or 30 gallons) with plenty of hiding spaces to accommodate their territorial needs.
  • Special Care Requirements: Rainbow Sharks have specific care requirements, including a need for certain water parameters and a varied diet, which may pose a challenge for beginner aquarists.

Before deciding to get a Rainbow Shark, make sure you’re well-equipped to meet their specific needs and can provide a compatible environment for them to thrive. rainbow shark2


Do Rainbow Sharks bite?

Rainbow Sharks typically don’t bite humans. However, they have been known to nip at the fins of other fish, particularly when defending their territory or if housed with incompatible tank mates.

Are Rainbow Sharks real sharks?

No, Rainbow Sharks are not true sharks. They’re freshwater fish belonging to the Cyprinidae family. They get their “shark” name due to their dorsal fin and torpedo-shaped body that resembles marine sharks.

Can Rainbow Sharks live with Bala Sharks

While Rainbow Sharks and Bala Sharks can both be kept in a home aquarium, they have different needs and temperaments. Bala Sharks are schooling fish that grow much larger than Rainbow Sharks, and Rainbow Sharks can be territorial, potentially leading to conflict. So, generally, they’re not recommended as tank mates.

Why is my Rainbow Shark not eating?

A Rainbow Shark might stop eating due to stress, illness, or incorrect water parameters. Changes in their environment, aggressive tank mates, or a diet lacking variety could also lead to loss of appetite. Check your water conditions and observe your fish’s behaviour to identify potential issues.

Why is my Rainbow Shark swimming upside down?

If your Rainbow Shark is swimming upside down, it might have swim bladder disease, which affects a fish’s buoyancy. This condition can be caused by various factors, including poor diet, sudden changes in water temperature, or bacterial infection. Consult a vet for appropriate treatment.

More Reading