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.

This product page combines six supplier size grades under one listing. Select the live size shown 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

Care point	Practical guidance
Accepted scientific name	Epalzeorhynchos bicolor (Smith, 1931)
Supplier name	Labeo bicolor, the original combination and an older trade synonym
Other clear common names	Red-tailed Black Shark, Redtail Shark and Redtail Sharkminnow
Care level	Moderate; suitable for a prepared keeper who understands territorial fish
Adult size	Approximately 12-15 cm; FishBase records 13 cm total length and OATA advises around 15 cm
Adult aquarium	At least 120 litres for one according to OATA; a longer 150-litre-or-larger aquarium is a more flexible community target
Social plan	Keep one Red Tail Black Shark in most home aquariums
Temperament	Semi-aggressive and territorial, particularly with maturity and around the lower aquarium
Temperature	Supplier range 23-27°C; a practical overlap with FishBase is 23-26°C
pH	Supplier range 6.0-7.8; aim for a stable 6.5-7.5 where practical
General hardness	Supplier range 5-20 dGH; OATA's group guidance is 4-12 dGH
Diet	Omnivorous; complete sinking food with algae-rich and vegetable variety plus measured frozen or live food
Aquarium region	Primarily lower to middle levels, with a regular patrol route around shelter and open lanes
Sale unit	One unsexed fish from the selected size grade

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. Petra's catalogue still uses the older Labeo wording, so both names are retained here with their roles explained instead of being presented as two different fish.

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. This distinction matters for search and care: 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 this listing does not target that ambiguous name. Our Rainbow Shark guide explains the comparison in more detail.

What the six size options mean

The live selector can show six supplier grades: 2-3 cm, 3-4 cm, 4-5.5 cm, 5.5-7 cm, 6-8 cm and over 9 cm. Stock and price belong to the selector because they can change independently for each grade. A size band is a commercial range, not a promise of an exact measurement, age, sex, rank or level of colour.

Selected grade	Planning point	Not guaranteed
2-3 cm	A small juvenile that still requires a complete adult housing plan	Beginner temperament, permanent small size or sex
3-4 cm	A juvenile; monitor feeding access and avoid large intimidating companions	Exact age or settled adult colour
4-5.5 cm	More visible body size, but territorial behaviour can still increase with growth	A community-safe adult
5.5-7 cm	Introduce to a fully prepared layout with hiding places already established	A proven temperament or individual selection
6-8 cm	A larger fish that needs adequate transport-day shelter and open swimming room	Sex, breeding condition or final size
Over 9 cm	A larger grade whose territorial needs should be treated as an adult-level concern	An exact length, age or mature sex

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 five retained gallery images

All five existing images remain attached in their original order. The first is the exact small supplier reference image associated with this product group. It supports supplier identity, but it is only 211 by 100 pixels at source and is not a photograph of the exact fish that will be dispatched. The remaining four are aquarium illustrations, not stock photographs.

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 supplier image is preserved as provenance; the scenes are clearly disclosed so they are not mistaken for documentary photography.

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.

Situation	Recommendation
Single specimen, lightly stocked	At least 120 litres with a mature filter, shelter and open swimming room
Community aquarium	A longer 150-litre-or-larger system gives more room to separate territories and feeding zones
Busy lower-level stocking	Increase the footprint or reconsider the shark; litres do not prevent competition for the same caves
Two Red Tail Black Sharks	Not recommended for an ordinary home aquarium; adults are territorial and OATA advises keeping them singly
Temporary juvenile setup	Only acceptable when the adult aquarium already exists and transfer is planned; sale size does not reset adult needs

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.

Element	Useful approach	Avoid
Substrate	Sand or fine rounded gravel that protects the mouth and barbels	Sharp gravel and waste-filled pockets
Shelter	Several stable caves, wood arches or shaded spaces	One contested cave for all bottom fish
Sight lines	Plants and wood that divide the lower aquarium into zones	A bare tank where every fish remains in view
Swimming room	An open route along the front or middle of the tank	Filling every centimetre with decor
Lid	A secure cover with cable and filter gaps closed	Open gaps that an active or startled fish can reach
Maintenance access	Space to siphon under and behind structures	Unmovable decor that traps food and waste

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

Petra records 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.

Parameter	Routine target	Action boundary
Temperature	23-26°C	Check the heater and thermometer if temperature moves unexpectedly
pH	6.5-7.5	Do not chase a number with sudden chemical dosing
General hardness	About 5-12 dGH where source water permits	Measure before altering mineral content
Ammonia	0 mg/l	Any detectable result requires immediate investigation
Nitrite	0 mg/l	Any detectable result is unsafe
Nitrate	No more than 20 mg/l above the tap-water baseline under OATA guidance	Review feeding, stocking and water changes if the trend rises

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.

Frequency	Task	What to observe
Daily	Count fish and check breathing, posture, fins, colour and appetite	Hiding, repeated chasing, rapid breathing or missed food
After feeding	Remove uneaten food and inspect the lower aquarium	Whether the shark and quieter tank mates both ate
Weekly	Test temperature, ammonia, nitrite, nitrate and pH	Actual readings and trends
Weekly	Carry out an appropriate partial water change with conditioned, temperature-matched water	Stable temperature and normal behaviour during and after the change
As required	Clean mechanical media in removed aquarium water and restore flow	Reduced output, trapped debris or noisy equipment
Monthly review	Inspect heater, thermometer, lid, cables, hoses and seals	Wear, drift and backup-equipment needs

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.

Food type	Role	Control point
Complete sinking pellet or wafer	Balanced staple delivered to the lower aquarium	Choose a size the fish can take cleanly
Algae-rich or spirulina food	Plant-rich variety that supports natural grazing behaviour	It does not turn the fish into a substitute for aquarium maintenance
Blanched vegetable	Occasional texture and plant matter	Offer a small portion and remove leftovers
Frozen or live food	Measured variety and feeding interest	Use a trusted source and avoid turning rich food into the whole diet
Natural algae and biofilm	Supplementary grazing surface	Cannot provide complete nutrition by itself

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.

Candidate type	Assessment
Active medium danios	Often a better fit when kept in the correct group and given open upper-level room
Robust medium barbs	Can work in a sufficiently large group and aquarium; avoid known fin-nipping pressure on slower fish
Suitable rainbowfish	Active open-water companions where adult size, group needs and water overlap are met
Calm but sturdy midwater fish	Case by case; confirm they will not be trapped or outcompeted
Other bottom dwellers	Higher risk because caves, substrate and sinking food are shared resources
Other freshwater “sharks”	Avoid as the default because body shape and territory overlap can trigger aggression

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.

Fish	Colour clue	Key planning difference
Red Tail Black Shark E. bicolor	Dark body with the red colour concentrated on the tail	Territorial; keep one in most home aquariums
Albino Rainbow Shark E. frenatum	Pale body with red colour on several fins	Different species and colour form; also territorial
Black Shark Labeo chrysophekadion	Dark body without the Red Tail Black Shark pattern	Much larger fish requiring a substantially larger specialist aquarium
Bala or Silver Shark Balantiocheilos melanopterus	Silver body with dark-edged fins	A large shoaling species, not a solitary territorial substitute

“Ruby Shark” should not be used as an SEO synonym for this product because it commonly points to Epalzeorhynchos frenatum. Clear entity boundaries are more valuable to customers and search engines than collecting every high-volume word into one listing.

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.

Observation	First response
Rapid breathing or hanging near flow	Test ammonia, nitrite, temperature and oxygenation; inspect equipment immediately
Persistent hiding and missed meals	Check bullying, shelter, water quality and recent changes
Faded body or tail	Review stress and environment rather than treating colour alone
Torn fins or abrasions	Identify aggression and sharp decor, then restore clean stable water
Weight loss despite interest in food	Isolate where appropriate and seek qualified fish-health advice
White spots, growths or unusual mucus	Quarantine and diagnose before medicating the display aquarium

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. Petra, however, does not provide a breeder certificate or a stock-specific breeding-origin field for this listing. The accurate boundary is therefore: the commercial trade is strongly associated with captive production, but this page does not invent a named breeder, farm, lineage or collection locality for the individual supplied.

Is this the right fish for your aquarium?

Good fit when	Poor fit when
The aquarium is mature, at least 120 litres and has a useful horizontal footprint	The aquarium is new, small, tall and narrow, or already crowded
You want one active territorial feature fish and can plan around it	You want a pair, group or several similar “sharks”
Tank mates are robust, active and occupy compatible zones	The community relies on timid bottom dwellers, shrimp or slow long-finned fish
The layout has several shelters, broken sight lines and open swimming room	The lower aquarium has one cave or no visual separation
You test water, control feeding and can act on persistent chasing	You need a passive “algae cleaner” that requires no dedicated care

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, delivery and first-order discount

Use the live option menu for current size, price and availability. The descriptive copy does not hardcode a price because the six grades can change separately. 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.

Eligible livestock orders are covered by the Live Arrival Guarantee subject to the current destination, delivery, evidence and reporting conditions on the delivery and returns pages. Eligible first-time customers can use WELCOME10 for 10% off at checkout, subject to the current discount terms. Check the special offers page rather than relying on an expired promotion copied into a product description.

Evidence and care sources

This listing separates supplier-specific facts from general species guidance. Petra supplies the common name, older Labeo bicolor identity, six size grades, a 12 cm growth figure and the recorded water range. External sources support the accepted taxonomy, broader adult planning and husbandry boundaries.

• 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 the supplier's range and general care guidance differ, the page shows the distinction and recommends a stable conservative overlap rather than hiding the variation.

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. This listing avoids that ambiguous keyword.

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. The supplier records 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 supplier reference 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.

Does the Live Arrival Guarantee and WELCOME10 apply?

Eligible livestock orders are covered subject to the current delivery and returns terms. Eligible first-time customers can use WELCOME10 for 10% off at checkout, subject to the current discount conditions.