Can Boeseman's Rainbowfish and Harlequin Rasbora Live Together?

Boeseman's Rainbowfish is a peaceful species (2/10), while Harlequin Rasbora is peaceful (1/10). This modest difference means Boeseman's Rainbowfish may occasionally assert dominance over Harlequin Rasbora.

Boeseman's Rainbowfish and Harlequin Rasbora both frequent the Top (Surface) and 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: Boeseman's Rainbowfish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 26°C and 28°C. Aim for the midpoint of this range (around 27.0°C) for optimal comfort.

Both fish can tolerate a pH between 7 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 9–12 dGH. Regular testing will ensure conditions stay within this range.

To house Boeseman's Rainbowfish 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 - lighly covered, Plants - Densely covered, Leaf Litter/Blackwater. Meeting these requirements will help both species thrive.

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