Can Harlequin Rasbora and Malawi Eyebiter Live Together?

Harlequin Rasbora is a peaceful species (1/10), while Malawi Eyebiter is semi-aggressive (8/10). This notable difference means Malawi Eyebiter may occasionally assert dominance over Harlequin Rasbora.

Large aggression gap (7 points) between Harlequin Rasbora and Malawi Eyebiter increases stress risk for the more peaceful fish.

Harlequin Rasbora and Malawi Eyebiter both frequent the Middle (Open Water) and Top (Surface) 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: Malawi Eyebiter is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 23°C and 28°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

The pH requirements of Harlequin Rasbora (5–7.5) and Malawi Eyebiter (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 10–12 dGH. Regular testing will ensure conditions stay within this range.

To house Harlequin Rasbora and Malawi Eyebiter together, plan for an aquarium of at least 475 litres with a minimum length of 150 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.

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.

Harlequin Rasbora and Malawi Eyebiter are the kind of pair that can look acceptable in a shop but become a maintenance problem at home. The main risk is not a single number in the chart; it is the way incompatible behavior, water needs, or pressure on space compounds over time once both fish are established in the same tank.