Can Sailfin Molly and Sepik Rainbowfish Live Together?

Sailfin Molly is a generally mild-mannered species (3/10), while Sepik Rainbowfish is peaceful (2/10). This modest difference means Sailfin Molly may occasionally assert dominance over Sepik Rainbowfish.

Sailfin Molly and Sepik Rainbowfish 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: Sepik Rainbowfish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

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

Hardness requirements are incompatible: Sailfin Molly needs 15–30 dGH while Sepik Rainbowfish requires 4–12 dGH.

To house Sailfin Molly and Sepik Rainbowfish together, plan for an aquarium of at least 110 litres with a minimum length of 90 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: Established Algae (Otocinclus), Plants - Densely covered. 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.

Sailfin Molly and Sepik Rainbowfish 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.