Red Tail Shark: Species Profile

Category: Freshwater Shark

Common Names: Red Tail Shark

Scientific Name: Epalzeorhynchos bicolor

Family: Cyprinidae

Minimum Tank Size: 55 Gallons

Care Level: Moderate

Temperament: Semi-Aggressive

Max Size: 4 Inches

Temperature: 72-80 F

pH: 6.5-7.5

Tank Level: Bottom

Colors: Black, Red

Diet: Omnivore

Breeding: Difficult

Red-tailed Shark on a Rock

Species Overview

From its name and appearance alone, the Red Tail Shark is a captivating fish. With a solid black body that abruptly shifts to bright red at the tail, this little freshwater fish seems to swim with a warning sign boldly stamped on its caudal fin. Despite lessening populations in the wild, this fish remains popular and accessible in the aquarium market.

While the personality and aggression that you would expect from such a brazenly colored fish do play a key role in raising a Red Tail Shark, an intermediate fish keeper can find success with this fish in the right conditions.

Distinguishing Features

You will find the Red Tail Shark in only one variety with a very consistent marking and shape. Every member of the Epalzeorhynchos bicolor species will mature to have dark black bodies and forked, red caudal fins. This red tail can provide powerful flicks to speed this fish through the water.

Contrasting this fish from the Rainbow Shark, every other fin, including the dorsal, pectoral, pelvic, and anal fins, is the same black shade as the body. Some Red Tail Sharks may have a faint white tip on the dorsal fin.

To earn them the title of Red Tail Shark, these fish all bear a triangular dorsal fin. Though this resembles a shark, these creatures have no further relationship to the saltwater predators. To the shark lover’s dismay, these creatures have closer connections to the carp than the shark.

Each Red Tail Shark has a downturned snout to help it scavenge for algae. On either side of the pointed snout, they have barbels to sense prey.

Red Tail Shark on Gravel


This small fish once flourished in the Chao Phraya River and basins of Thailand. It is documented that Red Tails were found in freshwater areas like lowland creeks, rivers, and streams.

These native regions have many qualities that can be successfully replicated in fish tanks. The substrate in native water was filled with rocks and sand with fast-moving currents that Red Tail Sharks enjoy. The murky Chao Phraya River contains decaying plant matter and bacteria, which causes the pH to become slightly acidic.

There was once an abundant supply of Red Tail Sharks in the wild as they occupied the largest river in Thailand. Now, almost all of the population is bred and cared for in captivity.

In 1996, the species was considered to be extinct in the wild until populations were rediscovered in 2011 and 2014. Now, these little creatures are considered critically endangered in their native environment.


As a medium-sized freshwater fish, the Red Tail Shark usually grows to be 4 or 5 inches long. Some have even been documented to reach 6 inches. Since females are larger than males, it can be expected that they will more likely reach this slightly larger size.

A full-grown Red Tail Shark should finish development by 15 months old. Before this, the fry and juvenile fish will be smaller and less deeply colored.


Red Tail Sharks are considered to be hardy fish. With proper care and conditions, a fish keeper can expect their fish to live a long life.

The average lifespan of Red Tails is between 5 and 8 years. However, as one of these fish reaches old age, the coloring may lose its vibrance, with scales fading to a pale gray and dull red.


Females of this species will mature to be larger and rounder than full-grown males. Adult males can have brighter red tails and a slimmer appearance.

The most discernible difference between males and females is the differently-shaped dorsal fin. A male’s dorsal fin will reach a sharper point while a female fin forms a right angle with her back.

These gender differences will present themselves once the Red Tail Shark is fully mature or over 15 months old.


A Red Tail can be a very active fish though it prefers to remain in its territory at the bottom of a tank. These fish enjoy exploring their surroundings and swimming against currents to increase activity. Having a tank that allows them to exercise their curiosity and their energy will ensure that they remain content.

Perhaps the defining feature of a Red Tail Shark is its ornery temperament. Both males and females of this species can be aggressive if their space undergoes an invasion.

Red Tail Sharks seem to be the most aggressive towards other Red Tails. It is common for two Red Tails in one tank to chase each other to death in a few weeks or months of being together.

The motivation for aggression in these fish is a strong sense of territory. If any fish invades the space that a Red Tail considers to be its home, they will chase and bully the fish throughout the tank to protect themselves.

While these fish do not prey on other fish, they are not afraid to make their presence known to any possible threats.

Another serious consideration regarding the behavior of these lively creatures is that they may continue to assert dominance even after their territory is cleared of invaders.

Since the lives of other fish could be at risk in an overcrowded tank, it is beneficial to keep a Red Tail Shark happy so that it does not tend towards bully behavior like this.

The fierce defense of its territory shows how much a Red Tail Shark values its privacy and independence.

When the tank is peaceful and properly separated, this little fish can enjoy exploring the bottom of the tank with plenty of hiding spots to feel secure and safe. With proper precautions, a happy Red Tail may never lash out to tank mates and can live a peaceful life.

Red-tailed Shark on a Driftwood

Tank Parameters

To properly recreate the natural preferences of these fish in the wild, there are many elements such as tank size, substrate type, lighting, and pH that will ensure that Red Tail Sharks can thrive in their captivity.

Minimum Tank Size

This species requires a tank that holds at least 55 gallons of water. Additionally, an elongated tank is preferable for Red Tails to allow sufficient exploration and territory marking.

Water Parameters

These fish must live in freshwater tanks that undergo frequent partial changes to keep the water clean.


The ideal temperature for Red Tail Sharks is between 72 and 80 degrees Fahrenheit. If it is ever necessary to shift the temperature within this range, change should happen gradually. A Red Tail could suffer shock from sudden changes in its environment.


The ideal level for these fish is between 6 and 8 pH. Since decaying plant matter makes the natural environment slightly acidic, it is best to replicate this measure in the tank.


These fish prefer a water hardness of between 10 and 15 KH.

Tank Setup

Red Tails become very possessive over the environment they live in, so providing adequate decorations and conditions will ensure that this fish is comfortable and free of stress.


This fish will thrive with various-sized rocks and pebbles on the tank’s floor. Fine gravel may pose a hazard since Red Tails like to graze the substrate looking for food and may ingest small particles.

This species prefers darkness, so darker-colored rocks may help it to feel comfortable. However, lighter-colored pebbles can help the dark fish to stand out in the tank.


The addition of plants and cave-like hiding spots to a tank will supply a Red Tail with plenty of spaces to hide and explore. Driftwood is a great option to provide surfaces to swim under and hide in. Objects that cast shadows and provide nooks to swim in are ideal for this fish.

Be sure to examine the tank once all decorations are placed to make sure that the Red Tail still has enough space to swim.


Fake plants that provide adequate cover will make a Red Tail the happiest. Some good options are Amazon Sword plants, Water Wisteria, and other fine-leaved plants.


It is necessary to avoid bright lights in a tank housing a Red Tail Shark. They are most active in dark and dim settings, so bright lights and direct sunlight should be completely avoided.


A filtration system that produces a heavy current is ideal for Red Tails. Filters can recreate the strong water currents this species enjoyed in their natural environment. These fish enjoy swimming against the current to release excess energy.


The tank should always maintain warm temperatures for a Red Tail Shark.

Red Tail Shark Swimming in Aquarium


The Red Tail Shark is an omnivore who enjoys scavenging food like algae and insect larvae. The down-turned mouth of this fish allows them to search for food throughout the day. This habit makes this fish an excellent exterminator and cleaner for the tank.

Since Red Tails prefer to stay at the bottom of the tank, sinking pellets are the best option for feeding. They will eat vegetables like zucchini and cooked peas or live food like bloodworms or daphnia.

Maintaining a wide variety of food that these fish consume can help to emphasize different behaviors in a fish and keep them active and curious.

A favorite pastime of the Red Tail is looking for food, and they are not picky eaters. However, if they do not finish feeding in a few minutes, they might be getting too much food. Ideally, this fish should be fed every other day to supplement the algae it finds in the tank.


Due to the antagonism that Red Tails exhibit toward other fish, including their own kind, it is virtually impossible for fish keepers to breed these fish in a tank at home.

Since Red Tail Sharks can cause another to die from incessant chasing, it is best to always keep these fish adequately separated. Additionally, Red Tails are known to consume their offspring or eggs, so even rare successful breedings might end poorly.

However, commercial breeders can encourage Red Tails to breed by increasing appropriate hormones to enable them to interact safely.

When breeding is successful, a female can carry up to 40 eggs at one time. Red Tail Shark fry will begin as transparent and increase in pale color until maturation at 15 months.

Common Diseases

While this fish is generally hardy, a few common ailments can be caused by environmental conditions. The diseases to look out for are ich and fin rot, both of which will eventually kill your Red Tail if left untreated.

Ich is a condition caused by a parasite called Ichthyophthirius multifiliis. If a Red Tail Shark develops this condition, it will show loss of appetite and may show white spots on the fins and body. To treat ich, the fish keeper should quarantine their Red Tail and slowly increase the water temperature enough to kill the parasite.

Red Tail Sharks are also susceptible to an infection called fin rot. This condition can be caused by dirty water and a lack of oxygen in the tank. A fish with fin rot will experience discolored fins, fraying, or complete loss of fins.

Potential Tank Mates

Though a Red Tail Shark can be territorial and aggressive, there are some fish that can coexist well with this fiery fish. The best options for tankmates are fish that are equally independent or those that have the protection of a school.

Fish which could be most vulnerable to Red Tail Sharks’ aggression are slow-moving, smaller, or timid. Betta fish, Fancy Guppies, and Angel Fish may pose as targets for sharks’ bullying.

Therefore, the best companions should be more lively, top-dwelling fish that can swim as fast as a Red Tail Shark. These qualities ensure that neither fish could overpower the other.

Some ideal tank mates that fit these criteria include Neon or Congo Tetras, Bala Shark, and Sparkling, Pearl, Dwarf, or Honey Gourami.