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The Unique Appeal of the Red Tail Black Shark

A striking focal point of any large aquarium, the Red Tail Black Shark (Epalzeorhynchos bicolor) is a unique fish with a semi-aggressive personality. Known for its large black body and vivid red tail, this species can grow up to 6 inches in length and typically lives 6–10 years. Rarely, some have been reported to live up to 18 years.

These fish are native to Thailand, though they are thought to be extinct in the wild due to poaching. They now thrive in the aquarium trade. Interestingly, the Red Tail Black Shark is more closely related to carp than to actual sharks, as it belongs to the Cyprinidae family.

My Experience With a Red Tail Black Shark

When I kept my 55-gallon planted aquarium, I had one of these stunning fish. He quickly became the unrivaled boss of the tank community. The Red Tail Black Shark claimed a cave as his territory, chasing away any tankmates that ventured too close.

• Tankmates like Zebra Danios (Zebra Danios care) and White Cloud Mountain Minnows (White Cloud Mountain Minnow care) displayed tight schooling behavior when my Red Tail Black Shark was nearby.
• Unfortunately, Swordtail fish (Swordtail care) did not fare well. One Swordtail was chased out of the tank entirely, which resulted in its tragic loss.

Aggression and Territorial Behavior in Red Tail Sharks

Caring for Red Tail Black Sharks isn’t too difficult, but selecting the right tankmates is crucial due to their semi-aggressive nature. They don’t inflict physical damage but can stress other fish with their territorial behavior.

• Ideal Tankmates: Semi-aggressive species that can stand up to the Red Tail Shark’s behavior, like Zebra Danios and White Cloud Mountain Minnows, work well.
• Avoid: Peaceful or docile fish like Swordtails, which can’t cope with their aggressive tendencies.

For more information about the species, check the detailed entry on Epalzeorhynchos bicolor.

Commonly Asked Questions About Red Tail Black Sharks

Are Red Tail Sharks Aggressive?

Yes, Red Tail Black Sharks are aggressive and territorial toward tankmates. It’s crucial to select semi-aggressive fish that can withstand this behavior.

To reduce aggression, consider the following:

• Provide plenty of hiding spaces: Driftwood, artificial caves, and plants will help break the line of sight.
• Ensure a large tank size: A 75–100+ gallon aquarium is recommended. The more space available, the less likely the Red Tail Shark will fixate on chasing other fish.

What Should I Feed My Red Tail Shark?

To keep your Red Tail Shark healthy, offer a balanced diet:

• Staple diet: High-quality flake or pellet food should be the base.
• Meaty foods (offered sparingly): Bloodworms, daphnia, brine shrimp, and krill.
• Vegetables (offered more frequently): Blanched zucchini, cucumber, peas, and occasionally, fruit.

How Often Should I Feed My Red Tail Shark?

A good rule of thumb is to feed your Red Tail Shark every other day. This reduces overfeeding and minimizes waste buildup in the tank.

Tank Requirements for Red Tail Black Sharks

To create a suitable environment for your Red Tail Black Shark, follow these guidelines:

• Temperature: 72–79°F
• pH: 6.8–7.5
• Water Hardness: 5–15 dH
• Water Flow: Fast, to replicate their natural habitat
• Substrate: Use gravel or large rocks. Avoid smaller gravel, as the shark might ingest it.

Live plants are a great addition to the tank since Red Tail Black Sharks don’t eat them. They may nibble on algae, but plants will remain unharmed.

Ideal Tankmates for Red Tail Black Sharks

Red Tail Black Sharks can be aggressive, so choosing the right tankmates is essential. Large-bodied and fast-swimming fish that occupy the mid-to-upper water column are ideal. Here are some recommended tankmates:

• Barbs
• Danios
• Angelfish
• Gouramis
• Tetras

Avoid housing them with Rainbow (Red Fin) Sharks (Rainbow Shark care) or any fish with red coloring, as this may trigger aggression. Additionally, don’t place peaceful or docile fish in the same tank, as they won’t survive long.

Breeding Red Tail Black Sharks

Breeding Red Tail Black Sharks in home aquariums is nearly impossible due to their aggressive nature. In the wild, they breed in rocky caves, but today they are bred on farms in Thailand using hormonal injections.

Key points about their breeding process:

• Females swell with eggs, and males develop a spawning tube before fertilization.
• The eggs hatch within 30–60 hours, and fry become free-swimming in 4 days.
• As they grow, fry change from silver to brown and finally to black. By 7–10 weeks, the signature red tail develops.

Red Tail Black Shark vs. Rainbow Shark

Though often confused, Red Tail Black Sharks and Rainbow Sharks have several differences. Here’s a breakdown:

Red Tail Black Sharks

• Only the tail is red; the rest of the body is deep velvet black.
• Inhabit the bottom and middle water column, coming to the surface only to feed.
• Prefer faster water flow.

Rainbow Sharks

• All fins are red, and their body is black or silver-black. An albino variety is available with pale white body and orange-red fins.
• Known for eating algae more efficiently than Red Tail Black Sharks.
• Prefer warmer temperatures (up to 81°F) and sand substrate to protect their delicate skin.
• Swim closer to the bottom and prefer moderate water flow.

For more details on Rainbow Sharks, check this Rainbow Shark guide.

This video provides more information about Red Tail Shark care:

Where to Find a Red Tail Black Shark and What to Look For

You can find Red Tail Black Sharks at local fish stores, larger pet store chains, or online vendors that deliver directly to your door. When purchasing in person, here’s what to look for to ensure you’re getting a healthy fish:

Signs of a Healthy Red Tail Black Shark

• Good coloration
• Strong swimmer
• No distressed breathing or gulping
• Healthy fins and body condition

Young fish may appear more streamlined than adults, but there should be no visible bones. Look for bright, clear eyes and no parasites.

Signs of Stress or Ill Health:

• Pale colors or discoloration
• Distressed breathing
• Frayed fins or emaciated body
• Weak swimming

When assessing the tank environment, ensure it is well-maintained:

• Are there dead fish floating?
• Is the water cloudy?
• Do any fish look diseased?

If you notice these issues, consider buying from another store. Well-maintained tanks are a good indication of a quality fish shop.

For more details on setting up a suitable environment, check out this guide on planted aquariums.

Recommended Aquarium Gear for Red Tail Black Sharks

A proper setup makes all the difference in keeping your red tail black shark healthy, active, and stress-free. Here are a few essentials to consider:

Final Thoughts on Owning a Red Tail Black Shark

I enjoyed keeping my Red Tail Black Shark, despite the occasional trouble he caused. In hindsight, I would have built the community around this fish, as its territorial nature posed risks to more peaceful tankmates.

With proper planning and careful tank setup, the Red Tail Black Shark can be a stunning addition to a well-planted aquarium.

Frequently Asked Questions (FAQ)

You probably won’t choose a fish based on the first letter of its name, but it can be fun and educational to explore. All fish have both common and scientific names, and the names listed here include both. Many fish have multiple common names but only one scientific name.

If a description intrigues you, explore further by looking up the fish by its scientific name. For example, if Adolfo’s Cory interests you, search for Corydoras adolfoi. This ensures you find the correct fish when shopping.

Most Intriguing Fish Starting With the Letter A

Not all fish are ideal for community tanks, but many are worth learning about. Here are some intriguing fish whose names start with the letter A.

Adolfo’s Cory (Corydoras adolfoi). The scientific name for this freshwater fish comes from the Greek korus (helmet) and dora (skin or hide), likely referring to the orange and black helmet it bears, along with the plates on its sides. Native to Rio Negro in equatorial Brazil, this attractive fish is known as peaceful, playful, and friendly, often getting along with other fish.

African Knifefish (Xenomystus nigri). Found in central African coastal rivers, this fish compensates for its bland appearance with extraordinary traits. It lacks a dorsal fin, and its anal and caudal (tail) fins are joined, allowing it to swim backward. It can also use its swim bladder to make a barking sound!

Albino Red-Tailed Shark (Epalzeorhynchos bicolor). This attractive species, primarily from the Chao Phraya River in Thailand, features a dark gray to black body with a large, bright orange tail. It is highly endangered in the wild and was declared extinct in the mid-1990s, though small populations have since been found. [Insert paragraph break here] Warning: Seek expert advice before keeping this fish with others, as they can be challenging in community settings.

Alligator Gar (Atractosteus spatula). Unsuitable for home aquariums, the Alligator Gar is one of the largest freshwater fish in North America, usually reaching 6.5 feet and 100 pounds, but it can grow much larger. Its long, tooth-filled snout and torpedo-shaped body make it resemble alligators, though no attacks on humans have been reported.

American Eel (Anguilla rostrata). Found in Greenland and along the eastern coast of Canada, the United States, and south to Trinidad, this species migrates to the Sargasso Sea to spawn. It can live for more than 40 years and may take 40 years to reach sexual maturity.

Angel Fish (Pterophyllum scalare). Among the most popular aquarium fish, it has a disc-shaped body, stunning spiny rays, and a large, triangular dorsal fin. Male and female partners team up during the brooding cycle to protect their eggs.

More Fish With Names That Start With A

While it’s not comprehensive, this list should provide plenty of ideas for expanding your home aquarium.

• Aba Aba (Gymnarchus niloticus)
• Ablabes Barb (Barbus ablabes)
• Adonis Characin (Lepidarchus adonis signifer)
• Adonis Pleco (Acanthicus adonis)
• Adonis Tetra (Lepidarchus adonis)
• African Blockhead Cichlid (Steatocranus casuarius)
• African Brass Tetra (Brycinus humilis)
• African Broad-Band Darter (Nannocharax parvus)
• African Butterfly Cichlid (Anomalochromis thomasi)
• African Glass Catfish (Pareutropius buffei)
• African Moon Tetra (Bathyaethiops caudomaculatus)
• African Peacock Cichlid (Aulonocara nyassae)
• African Pike-Characoid (Hepsetus odoe)
• African Red-Eyed Characin (Arnoldichthys spilopterous)
• African Tiger Fish (Hydrocynus goliath)
• African Whiptail Catfish (Phactura ansorgii)
• African Wood Catfish (Chrysichthys ornatus)
• Agassiz’s Dwarf Cichlid (Apistogramma agassizii)
• Ahl’s Rummy Nose Tetra (Hemigrammus rhodostomus)
• Akure Aphyosemion (Fundulopanchax gardneri)
• Alabama Hog Sucker (Hypentelium etowanum)
• Albert’s Synodontis (Synodontis alberti)
• Albino Driftwood Cat (Auchenipterus nuchalis)
• Albino Fetivum (Mesonauta festiva)
• Albino Ram (Microgeophagus ramirezi)
• Albino Tiger Barb (Barbus tetrazona)
• Algae Eater, False Siamese (Epalzeorhynchos sp)
• Algae Eater, Lemon (Gyrinocheilus aymonieri)
• Algae Eater, Siamese (Crossocheilus siamensis)
• Altum Angel (Pterophyllum altum)
• American Flagfish (Jordanella floridae)
• Amur Catfish (Pelteobagrus fulvidraco)
• Angelicus (Synodontis angelicus)
• Anostomus (Anostomus anostomus)
• Ansorge’s Neolebias (Neolebias ansorgii)
• Apollo Shark (Luciosoma trinema)
• Arapaima (Arapaima gigas)
• Arched Corydoras (Corydoras arcuatus)
• Archer eelpout (Lycodes sagittarius)
• Archerfish (Banded) (Toxotes jaculatrix)
• Archerfish (Common) (Toxotes chatareus)
• Armor Bill Tetra (Phago loricatus)
• Armored Catfish (Callichthys callichthys)
• Armoured Bichir (Polypterus delhezi)
• Arowana (Osteoglossum bicirrhosum)
• Arulius Barb (Puntius arulius)
• Asian Arowana (Scleropages formosus)
• Asian Bumblebee Catfish (Leiocassis siamensis)
• Asian Redtailed Catfish (Hemibagrus wyckioides)
• Asiatic Knifefish (Notopterus notopterus)
• Atlantic Mudskipper (Periophthalmus barbarus)
• Atlantic Sturgeon (Acipenser sturio)
• Auratus (Melanochromis auratus)
• Aurora Cichlid (Pseudotropheus aurora)
• Australian Bass (Macquaria novemaculeata)
• Australian Lungfish (Neoceratodus forsteri)
• Australian Pearl Arowana (Scleropages jardini)
• Australian Rainbowfish (Melanotaenia fluviatilis)
• Australian Spotted Arowana (Scleropages leichardti)
• Australian Swamp Eel (Ophisternon gutturale)
• Axelrod’s Corydoras (Corydoras axelrodi)
• Axelrod’s Rainbowfish (Chilatherina axelrodi)
• Azureus Cichlid (Copadichromis azureus)

Family	Cobitidae
Origin	Southeast Asia
Social	Peaceful
Tank Level	Bottom
Minimum Tank Size	15 gallons
Diet	Omnivore, enjoys live foods
Breeding	Egglayer
Care	Intermediate
pH	6.0 to 6.5
Hardness	up to 10 dGH
Temperature	75 to 86 degrees F (24 to 30 degrees C)

Origin and Distribution

Originating from Southeast Asia, the coolie loach is indigenous to the streams of Borneo, Java, western Malaysia, Singapore, Sumatra, and Thailand. Originally named Cobitis kuhlii, and later changed to Acanthophthalmus kuhlii, the current scientific name of this fish is Pangio kuhlii. Many references still utilize former scientific names.

Pangio kuhlii is one of two dozen species of kuhlis, a number of which closely resemble each other. The subspecies Pangio kuhlii sumatranus and Pangio kuhlii myersi have been described based on differences in coloration and markings. P. sumatuanus (also known as the Sumatra Kuhli) has fewer and darker bands than Pangio kuhlii. Sporting even wider bands is the Pangio kuhlii myersi. Although Pangio kuhlii remains the most popular and readily available of the coolie loaches, it is not unusual to purchase an incorrectly named loach.

Colors and Markings

Coolie loaches have an eel-like body that is yellow to pink in color, with multiple dark brown bands or stripes that partially or fully encircle the body. The body and stripe color patterns vary based on subspecies. The coolie loach possesses no lateral line, the fins are small, and the dorsal fin is located on the lower third of the body, much closer to the tail than the head.

The eye of the coolie is covered by a thin layer of transparent skin and is hidden under one of the dark bands. Below the eyes are a pair of sharp spines that rise if the fish is threatened, making it difficult for a predator to swallow them or for an owner to net them; take special care when doing so. The mouth of the coolie loach points downward and is surrounded by four pairs of barbels.

Tankmates

Coolie loaches are happiest when kept in groups of a half-dozen or more other coolies, and they are easily kept with non-aggressive fish. When kept singly they are quite shy and will remain hidden most of the time. Avoid keeping coolies with large or territorial fish, such as cichlids; instead choose small fish such as danios, rasboras, and tetras.

Coolie Loach Habitat and Care

In nature, the coolie loach lives in locations where there is clear, slow-moving water running over sand. They will tolerate a range of water parameters but prefer water on the acidic side with slightly colder temperatures in the mid-70s Fahrenheit. The smooth substrate is a must as these obligate burrowers will be injured by substrates having rough edges. Sand is the preferred substrate for these fish.

Make sure the tank is tightly covered as coolie loaches will jump out of the tank, particularly when startled. The inlet tube on the filter needs to also be covered with mesh or a sponge, as there are many documented cases of loaches swimming up the inlet tube and getting trapped in the filter. Owners have reported cases in which coolie loaches have disappeared for months, only to be found under the UGF or inside a canister filter, still very much alive. Take a headcount on your coolies to ensure you haven’t lost one or the lost fish may suffer and starve.

Coolie tanks should have plenty of safe hiding places, preferably in low, live plants when possible. Rocks, driftwood, and caves are all the best decor for coolie loaches. Keep lighting subdued, however, a well-lit tank is suitable as long as it is heavily planted, thus offering shady places for the loaches to hide. Place a moonlight in the tank so you can observe their nocturnal activities.

Coolie Loach Diet and Feeding

Live foods are the preferred diet for coolie loaches. However, they will accept a variety of foods, including frozen, freeze-dried, tablets, wafers and flake foods. The key is to remember that they need smaller foods that will sink. Always feed coolies at night.

When it comes to live foods, bloodworms are readily accepted as well as glass worms, tubifex, and daphnia. Frozen versions of these foods are the next best option. Feed live or frozen foods a couple of times per week to augment dry foods.

Gender Differences

There are no readily discernible differences between coolie loaches when they are not breeding. Some hobbyists have observed that males have larger pectoral fins, with thickening of the second ray. Once females are carrying eggs they become noticeably larger, sometimes in the extreme. In some cases, it’s even possible to see the green-colored eggs through the skin of the female’s abdomen.

Breeding the Coolie Loach

Breeding of coolie loaches is challenging, but it has happened in captivity. The breeding tank should have low water levels, very dim lighting, and floating plants, which will be used by the female when laying her eggs. Water pH should be about 6.5, and the water hardness should be lowered. Dense vegetation will help promote spawning. The more comfortable the coolies become with their environment, the greater the chance of spawning.

Because coolies are communal spawners, keeping a larger group will increase the likelihood of spawning. Fish do not reach sexual maturity for two years, which means you may have to be patient if your fish are young when you purchase them. Condition the fish with plenty of live food to encourage spawning.

As females near the time to lay their eggs, they will grow very large. When ready to spawn, the female will release bright green adhesive eggs, usually on the underside of the floating plants. To ensure the greatest number of fry survive, remove the adult fish to their original tank once the eggs have been laid.

Eggs will hatch in approximately 24 hours, and they can number up to several hundred. Infusoria, generally present in mature live plants, is an ideal first food. Freshly hatched brine shrimp are also a good first food. Commercially prepared fry food or finely crushed flakes are suitable as food for coolie loach fry.

More Pet Fish Species and Further Research

If coolie loaches appeal to you, and you are interested in some compatible fish for your aquarium, check out:

Check out additional fish breed profiles for more information on other freshwater fish.