Can Japanese Ricefish (Medaka) and Norman's Lampeye Killifish Live Together?

Japanese Ricefish (Medaka) is a peaceful species (2/10), while Norman's Lampeye Killifish is peaceful (1/10). This modest difference means Japanese Ricefish (Medaka) may occasionally assert dominance over Norman's Lampeye Killifish.

Japanese Ricefish (Medaka) and Norman's Lampeye Killifish 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 22°C and 28°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 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 5–15 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Japanese Ricefish (Medaka) and Norman's Lampeye Killifish together, plan for an aquarium of at least 46 litres with a minimum length of 45 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, 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.