Can Harlequin Rasbora and Julii Corydoras (False Julii) Live Together?

Harlequin Rasbora is a peaceful species (1/10), while Julii Corydoras (False Julii) is peaceful (0/10). This modest difference means Harlequin Rasbora may occasionally assert dominance over Julii Corydoras (False Julii).

In terms of spatial distribution, Harlequin Rasbora prefers the Middle (Open Water) and Top (Surface) zones, whereas Julii Corydoras (False Julii) occupies the Bottom (Substrate) zone. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

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 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 2–12 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Harlequin Rasbora and Julii Corydoras (False Julii) together, plan for an aquarium of at least 72 litres with a minimum length of 60 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, Leaf Litter/Blackwater, Sand (Sifters). 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.