Can Denison Barb (Roseline Shark) and Harlequin Rasbora Live Together?

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

Denison Barb (Roseline Shark) and Harlequin Rasbora 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.

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

The safe temperature window for both species falls between 22°C and 26°C. Aim for the midpoint of this range (around 24.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–12 dGH. Regular testing will ensure conditions stay within this range.

To house Denison Barb (Roseline Shark) and Harlequin Rasbora 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.

Providing a mix of open swimming space and sheltered areas with rocks, driftwood, or plants will keep both species comfortable and allow natural behaviour.

Specific environmental needs for this combination include: Plants - Densely covered, Driftwood (Digestion/Hiding), Smooth Gravel (Sensitive Barbels), Leaf Litter/Blackwater. 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 Harlequin Rasbora's requirement for live plants. Compromise where possible or prioritise the more critical need.

Both species do well with high (river/stream) water movement, so a standard filtration setup rated for the tank volume should suffice.