Can Balloon Molly and Japanese Ricefish (Medaka) Live Together?

Balloon Molly is a generally mild-mannered species (3/10), while Japanese Ricefish (Medaka) is peaceful (2/10). This modest difference means Balloon Molly may occasionally assert dominance over Japanese Ricefish (Medaka).

Balloon Molly and Japanese Ricefish (Medaka) both frequent the 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: Japanese Ricefish (Medaka) 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 and 8.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 12–25 dGH. Regular testing will ensure conditions stay within this range.

To house Balloon Molly and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 75 litres with a minimum length of 60 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, Plants - Floating. Meeting these requirements will help both species thrive.

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