Red Tail Black Shark (Epalzeorhynchos bicolor)

The Red Tail Black Shark (Epalzeorhynchos bicolor) is a dark-bodied freshwater cyprinid with a vivid red caudal fin and a confident, shark-like swimming style. It is not a true shark. It is a territorial tropical fish from the minnow and carp family, best chosen for a mature, well-structured aquarium where one specimen can establish a territory without dominating every other fish.

Choose from the six listed size grades in the option menu, then choose the quantity. Each quantity is one unsexed fish; no option promises a male, female, pair, exact age or exact individual. Juveniles can look less intensely black after transport or under bright lighting, but the adult aquarium must still be planned around the species' full size and territorial behaviour.

Red Tail Black Shark at a glance

Identity: a cyprinid, not a true shark

The current accepted name is Epalzeorhynchos bicolor. Eschmeyer's Catalog of Fishes records that the species was originally described as Labeo bicolor by Smith in 1931 and now treats that name as the original combination under the valid species Epalzeorhynchos bicolor. The older Labeo name remains common in aquarium trade records; both names refer to this species.

The word “shark” describes the fish's profile, upright dorsal fin and active movement. It is a ray-finned freshwater fish in Cyprinidae, not a marine or freshwater member of the true shark lineage. For care, this means a Red Tail Shark needs normal tropical freshwater husbandry, biological filtration and species-appropriate companions, not a specialist marine system.

The body-and-fin pattern is also diagnostic. The classic Red Tail Black Shark has a dark body and a red or orange-red tail, while the Rainbow Shark, Epalzeorhynchos frenatum, generally carries red colour on several fins. “Ruby Shark” is commonly used for the Rainbow Shark, not reliably for this species, so that name should not be used to identify this fish. Our Rainbow Shark guide explains the comparison in more detail.

What the six size options mean

The size selector lists six grades: 2-3 cm, 3-4 cm, 4-5.5 cm, 5.5-7 cm, 6-8 cm and over 9 cm. Check the selector for current availability and price for each grade. A size band is a commercial range, not a promise of an exact measurement, age, sex, rank or level of colour.

Do not buy a smaller grade as a way to postpone the correct aquarium. Use the tank volume calculator with the aquarium's internal dimensions and keep the permanent footprint, filtration and stocking plan in view from the start.

How to read the gallery

The first gallery image is a small reference image, not a view of the exact fish that will be dispatched. The other four are aquarium illustrations. Use the scientific name and written offer to confirm what is sold; gallery scenes do not guarantee the appearance of an individual fish.

The illustrations should be used only for a broad sense of a shark-like body and red-tail colour direction. They are not reliable identification plates: some show body or fin colour that does not perfectly match the accepted dark-body, red-tail pattern. One illustration contains two fish; that is an artistic scene and not a recommendation to keep a pair. The option menu still supplies one fish per quantity.

• No image guarantees the exact individual, sex, size, shade, fin shape or marking supplied.
• Temporary transport stress, aquarium background, lighting and age can alter visible colour.
• Use the written identity and accepted scientific sources, not an illustration, to distinguish this species from a Rainbow Shark.
• The gallery shows the species and illustrative scenes, not the exact fish supplied.

Adult size and minimum tank size

FishBase records a maximum length of 13 cm total length, while OATA advises that Red-tailed Black Sharks grow to around 15 cm. The difference is small enough to plan conservatively around a solid 15 cm adult. Body length alone understates the space requirement because this fish patrols, accelerates and defends a lower-level territory.

OATA recommends an aquarium of at least 120 litres for a Red-tailed Black Shark. That is a welfare floor for one fish, not a target for ambitious stocking. A longer aquarium around 150 litres or more usually provides a more useful footprint for caves, visual barriers, robust tank mates and an open route to swim. An aquarium with generous length is preferable to a tall narrow tank of the same volume.

Territorial behaviour and social plan

Young fish may appear reasonably peaceful, but territorial behaviour often strengthens as the fish matures. A settled specimen can claim a cave, a route between wood and rocks, or a feeding area. Chasing is most likely when another fish repeatedly enters that zone, resembles another freshwater “shark”, or competes for the same lower-level shelter.

The safest default is one Red Tail Black Shark per aquarium. Keeping a pair does not create a social benefit, and casual group keeping can produce repeated pursuit and injury. A large specialist system may change the amount of available territory, but it does not change the species' adult behaviour enough to make multiple fish a routine recommendation.

Normal boundary-setting should not become constant harassment. Repeated high-speed pursuit, a tank mate pinned in one corner, damaged fins, missed meals or a fish that cannot leave cover are signs that the stocking or layout is failing. Use the tank-mate planning tool as a first screen, then assess the exact adult size, speed, aquarium zone and temperament of every species.

Aquarium layout: territory without a dead end

A successful layout combines shelter with open swimming room. Use smooth rocks, stable wood, robust plants and more than one cave-like retreat. Break long sight lines so the shark does not monitor the entire aquarium from a single position. At the same time, leave a clear lane for movement and enough access to clean behind the hardscape.

Plants are useful for cover and visual separation, but the species does not require a heavily planted aquarium. Choose robust plants that tolerate the selected light and water conditions. Secure newly planted stems and keep enough bare substrate visible to monitor waste and feeding.

Water parameters and stability

Our stock records show 23-27°C, pH 6.0-7.8 and 5-20 dGH for this stock. FishBase gives 22-26°C and pH 6.5-7.5, while OATA's broader freshwater-shark guidance gives 22-27°C, pH 6.5-8.0 and 4-12 dGH. A practical routine target is therefore 23-26°C, pH 6.5-7.5 and moderate hardness, without making abrupt corrections to a stable aquarium.

Use a mature biological filter and maintain good oxygen exchange. FishBase associates the species with rivers and floodplains; that ecological context supports clean, well-circulated water, but the aquarium does not need a punishing current. Diffuse the return so circulation reaches the whole tank without forcing the fish to fight a narrow jet. Compare your readings with the water parameter matcher before ordering.

Filtration and maintenance routine

The filter must be established before the fish arrives. A new aquarium is not made mature by bottled claims or by waiting a fixed number of days; test data and a functioning nitrogen cycle matter. Keep ammonia and nitrite at zero, record nitrate rather than guessing, and service mechanical media without destroying the biological population.

Feeding a Red Tail Shark well

FishBase describes Epalzeorhynchos bicolor as omnivorous, taking plant matter and small benthic animals. OATA recommends sinking pellets with a high algae content and suitable live or frozen foods such as bloodworm or brine shrimp. Use a complete sinking omnivore or algae-rich pellet as the regular foundation, then add measured vegetable and animal-based variety.

OATA advises one measured daily feed for freshwater sharks, limited to what is eaten within a few minutes. In a mixed aquarium, several small feeding points can stop one territorial fish from controlling every sinking item. Watch the food reach each animal rather than scattering extra “just in case”; overfeeding leaves waste exactly where this fish patrols.

Red Tail Shark tank mates

The best companions are active, robust fish that occupy different areas, tolerate the same water and are not easily intimidated. OATA specifically gives danios, barbs and rainbowfish as examples. That is a starting point, not permission to mix every member of those groups. Adult size, group size, fin shape, swimming speed and the aquarium footprint still need checking.

Avoid tiny, delicate, very slow or long-finned fish, ornamental shrimp, and timid bottom dwellers that cannot escape a defended zone. Corydoras and loaches are not automatic companions merely because they are community fish; in a small or crowded aquarium they may be chased whenever they cross the shark's route. Browse the wider tropical fish collection only after the territorial plan is settled.

Red Tail Black Shark vs similar aquarium fish

Common names around freshwater “sharks” are inconsistent. Compare scientific identity and adult requirements before buying by name alone.

“Ruby Shark” commonly refers to the Rainbow Shark, Epalzeorhynchos frenatum, a different fish with its own care needs.

Arrival, acclimation and first-week behaviour

Prepare the aquarium before dispatch. Test the water, confirm the heater and filter are working, close gaps in the lid and decide where the fish can shelter without being trapped. Read the current delivery information and Live Arrival Guarantee terms before the parcel arrives so the reporting process is understood in advance.

1. Inspect the closed package immediately and follow the current guarantee instructions if anything is wrong.
2. Keep the room calm and avoid exposing the transport bag to sudden heat, cold or bright light.
3. Follow the supplied acclimation guidance, using the acclimation timer if useful.
4. Transfer the fish without adding transport water to the display aquarium.
5. Keep lighting subdued and watch balance, breathing and the reaction of established fish.
6. Offer a small familiar food only after the newcomer has settled, then remove leftovers.

A new Red Tail Black Shark may hide, pale temporarily or explore repeatedly during the first days. The trend should move towards steady breathing, open fins, a regular patrol route and confident feeding. Constant frantic swimming, surface gasping or being attacked by resident fish is not normal settling.

Health monitoring and warning signs

Look for clear eyes, intact fins, a smooth body line, steady respiration and a full but not swollen abdomen. Colour alone is not a diagnosis because stress and lighting can make the body appear grey or the tail less intense. Combine any colour change with appetite, breathing, posture, skin, fins and water-test results.

Do not choose medication by keyword or appearance alone. Similar signs can result from water quality, injury, parasites, bacterial disease or social stress, while the wrong treatment can harm the biological filter and other livestock. Persistent or serious signs need advice from an aquatic veterinary professional or suitably qualified fish-health specialist.

Sexing and breeding context

OATA notes that freshwater sharks are difficult to sex. This listing therefore supplies unsexed fish and does not promise a breeding pair. Size, colour strength and fin shape should not be treated as reliable sex guarantees for a retail juvenile.

The ornamental trade breeds the species at commercial scale, but OATA considers home-aquarium reproduction unlikely because adults require territories that are difficult to provide together. Buying two fish does not create a breeding project; it is more likely to create territorial conflict. A specialist breeding programme would need much more space, controlled broodstock management and a plan for separating incompatible adults.

Conservation context and source boundaries

Epalzeorhynchos bicolor is native to Thailand. FishBase records river and floodplain habitat in the Chao Phraya basin, and a 2014 field paper reported the species again from the Mae Klong basin after a long period of serious concern about its wild status. That conservation history should not be used as scarcity marketing.

FishBase reports that ornamental exports are captive-bred, and OATA says most freshwater sharks in the trade are captive-bred because some wild species are threatened. This fish is not sold with documented breeder, farm, lineage or collection-locality details. Ask before ordering if traceable origin matters to your aquarium plans.

Is this the right fish for your aquarium?

If the fit remains uncertain, use the contact page before ordering and include aquarium dimensions, litres, water readings and the full current stock list. A clear “not for this tank” decision is better than relying on the fish's small sale size.

Ordering and delivery

Use the live option menu for current size, price and availability. Each grade can have a different price and availability. Review the full Loaches and Algae Eaters collection or broader freshwater fish guide when comparing alternatives, but do not treat every bottom-oriented species as compatible.

Review the current delivery, returns and live-arrival terms for your postcode before ordering.

Evidence and care sources

The references below support the species identity and broader care guidance; they do not document the origin or condition of an individual fish.

• OATA: How to look after freshwater sharks supports UK guidance for adult size, minimum volume, water, feeding, substrate, territorial behaviour and compatibility.
• FishBase: Epalzeorhynchos bicolor supports current identity, family, distribution, adult length, water, habitat, diet and solitary adult behaviour.
• Eschmeyer's Catalog of Fishes confirms that Labeo bicolor is the original combination and Epalzeorhynchos bicolor is the valid current name.
• Kulabtong and colleagues: rediscovery in western Thailand provides primary field evidence and conservation context for wild E. bicolor.

External sources describe the species, not the exact fish dispatched. Where ranges differ, use the stable conservative overlap described above and avoid abrupt water changes.

Frequently asked questions

Is a Red Tail Black Shark a real shark?

No. It is a tropical freshwater cyprinid in the minnow and carp family. The common name refers to its shark-like outline and movement.

What is the correct scientific name?

The accepted name is Epalzeorhynchos bicolor. Labeo bicolor is the original combination and remains common in supplier and aquarium-trade records.

Is Red Tail Shark the same fish?

Yes, when the name refers to Epalzeorhynchos bicolor. Redtail Shark and Red-tailed Black Shark are common-name variants, so check the scientific name whenever a retailer uses shortened wording.

Is Ruby Shark another name for this species?

Not reliably. Ruby Shark is commonly used for the Rainbow Shark, Epalzeorhynchos frenatum. These are different species.

How big does a Red Tail Shark get?

Plan for approximately 12-15 cm. FishBase records 13 cm total length and OATA advises that Red-tailed Black Sharks grow to around 15 cm.

What is the minimum Red Tail Shark tank size?

OATA recommends at least 120 litres for one. A longer aquarium around 150 litres or more gives better scope for territory, shelter and compatible community stocking.

Can I keep two Red Tail Black Sharks together?

Not as a routine home-aquarium plan. Adults are territorial and are best kept singly. The gallery image containing two fish is an illustration, not a pair-keeping recommendation.

Are Red Tail Black Sharks aggressive?

They are territorial rather than indiscriminate predators. Aggression commonly increases with maturity and is directed towards similar-shaped fish or animals entering the same lower-level territory.

Which tank mates are suitable?

Robust, active danios, suitable barbs and suitable rainbowfish can work when their exact group, adult size and water needs are met. Avoid tiny, timid, slow, long-finned and competing bottom-dwelling species.

Can a Red Tail Shark live with Corydoras or loaches?

Only with caution. They share the lower aquarium, caves and sinking food, so territorial pressure can become a problem even when the other species is normally peaceful.

Can it live with a Rainbow Shark?

That is not recommended as the default. Their similar shape, behaviour and preferred territory can create repeated conflict.

What does a Red Tail Shark eat?

Use a complete sinking food as the staple, with algae-rich and vegetable variety plus measured frozen or live foods. Natural algae and leftovers are not a complete diet.

What temperature does it need?

A practical target is 23-26°C. Our stock records show 23-27°C and FishBase records 22-26°C; stability matters more than pushing to an edge.

What pH is suitable?

A stable pH of 6.5-7.5 is a sensible target within the supplier and FishBase ranges. Avoid rapid chemical adjustments.

Is this species a good algae eater?

It grazes algae and plant-rich material, but it is an omnivore and still needs complete food. It should never be purchased as a replacement for cleaning, water changes or algae control.

Will the fish look exactly like the images?

No. The first image is a small reference image and the other four are illustrations. None shows the exact individual supplied, and some illustrative details are not reliable for species identification.

What does quantity one include?

Quantity one supplies one unsexed fish from the size grade selected. It does not include a pair or guarantee an exact measurement within the commercial band.

Where can I check delivery and live-arrival terms?

Check the current delivery and returns pages for postcode eligibility, live-arrival terms and reporting requirements before ordering.