Red Tail Shark
Epalzeorhynchos bicolor
Min Tank Size
200L
Adult Size
12 cm
Lifespan
8 years
About
Originally from Thailand, the red tail shark is now critically endangered in the wild, yet thrives as one of the hobby's most recognizable fish. That jet-black body paired with a vivid flame-red tail makes it an instant centerpiece, and juveniles sold at just a few centimeters look absolutely stunning under store lighting.
They grow to around 12 cm and develop a personality that catches a lot of beginners off guard. What looks like a peaceful bottom cruiser in a shop tank turns into a confident, territorial presence once it settles into your aquarium. 5 and moderate hardness.
They're not picky eaters at all. Sinking pellets, wafers, frozen bloodworm, blanched vegetables, and algae-based foods are all accepted readily. Feeding them a varied diet with some plant matter keeps them at their best.
The tank needs to be properly sized, at least 200 liters, and heavily decorated with caves, driftwood, and broken sightlines. Without visual barriers, this fish will chase and stress tankmates relentlessly.
It's a rewarding species when set up correctly, and seeing one confidently patrolling its territory in a well-aquascaped tank is genuinely impressive. If you want to see what a thriving red tail shark setup actually looks like, browsing community tank builds and journals from other hobbyists is a great way to get inspired.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Red Tail Shark together
Red Tail Shark is strongly territorial. Multiples fight over space unless the tank is large enough for each to claim its own area. A single individual is the safer default.
Compatibility
Fast-moving midwater and upper-level fish work best with red tail sharks. Rainbowfish, giant danios, larger barbs, and robust tetras generally do well because they spend little time in the shark's territory and can easily outrun a charge. Corydoras, plecos, and other bottom-dwelling species are risky, as are any fish with long flowing fins that might attract nipping. Avoid rainbow sharks entirely, and don't attempt to keep two red tail sharks under any circumstances. In tanks over 300 liters with excellent hardscape and broken sightlines, compatibility with semi-robust midwater species improves significantly. Dwarf cichlids that hold their own territory can sometimes work, but it's situational.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The biggest mistake beginners make is underestimating adult aggression after buying a small, seemingly docile juvenile. A 10 cm red tail shark in a sparsely decorated 150-liter tank becomes a bully fast. Tank size and decor density matter more than water parameters here. They're hardy fish once established, but they need hiding spots and visual breaks to stay manageable. Diet should include algae-based foods regularly, not just protein. Skipping plant matter leads to increased aggression in some fish. Also worth knowing: their true adult size surprises people who bought them expecting a small bottom dweller.
Behavior & Aggression
Red tail sharks are territorial by nature, and aggression escalates sharply when they perceive a threat to their claimed space. The worst conflicts happen with fish that share a similar body shape, dark coloring, or red markings, which is why other Epalzeorhynchos species like rainbow sharks are completely off the table as tankmates. Bottom dwellers get targeted too, especially if they overlap the same cave or feeding zone. Providing multiple caves and dense hardscape gives the shark a defined territory and reduces patrolling aggression toward other fish. Chasing is the most common behavior, but prolonged harassment can stress tankmates to death.
Things to Know
- Keep only one per tank, conspecifics will fight to the death
- Attacks other bottom dwellers and fish with similar body shape or coloring
- Needs heavy decor with caves and visual breaks to reduce aggression
- May harass slow or long-finned tankmates relentlessly
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