Can Blackline Rasbora and Frontosa Live Together?

Blackline Rasbora is a peaceful species (1/10), while Frontosa is moderately assertive (5/10). This notable difference means Frontosa may occasionally assert dominance over Blackline Rasbora.

Blackline Rasbora and Frontosa 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: Blackline Rasbora is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 23°C and 26°C. Aim for the midpoint of this range (around 24.5°C) for optimal comfort.

The pH requirements of Blackline Rasbora (6–7.5) and Frontosa (8–9) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 12–15 dGH. Regular testing will ensure conditions stay within this range.

To house Blackline Rasbora and Frontosa together, plan for an aquarium of at least 583 litres with a minimum length of 180 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, Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Sand (Sifters), Smooth Gravel (Sensitive Barbels). 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.

Blackline Rasbora and Frontosa 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.

Feeding time deserves special attention with this pairing. Blackline Rasbora is an aggressive eater that may prevent Frontosa from getting enough food.

Because Blackline Rasbora is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Frontosa receives an adequate share.