Can Cardinal Tetra and Denison Barb (Roseline Shark) Live Together?

Cardinal Tetra is a peaceful species (1/10), while Denison Barb (Roseline Shark) is generally mild-mannered (3/10). This modest difference means Denison Barb (Roseline Shark) may occasionally assert dominance over Cardinal Tetra.

Cardinal Tetra and Denison Barb (Roseline Shark) both frequent the Middle (Open Water) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

Worth noting: Denison Barb (Roseline Shark) is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

The safe temperature window for both species falls between 24°C and 26°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 and 7. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–8 dGH. Regular testing will ensure conditions stay within this range.

To house Cardinal Tetra and Denison Barb (Roseline Shark) together, plan for an aquarium of at least 240 litres with a minimum length of 120 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Densely covered, Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Denison Barb (Roseline Shark) is a plant destroyer, which conflicts with Cardinal Tetra's requirement for live plants. Compromise where possible or prioritise the more critical need.

Cardinal Tetra prefers Low (Still Water) flow while Denison Barb (Roseline Shark) needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

Feeding time deserves special attention with this pairing. Denison Barb (Roseline Shark) is an aggressive eater that may prevent Cardinal Tetra from getting enough food.

Because Denison Barb (Roseline Shark) is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Cardinal Tetra receives an adequate share.