Can Dwarf Rasbora and Japanese Ricefish (Medaka) Live Together?

Dwarf Rasbora is a peaceful species (1/10), while Japanese Ricefish (Medaka) is peaceful (2/10). This modest difference means Japanese Ricefish (Medaka) may occasionally assert dominance over Dwarf Rasbora.

In terms of spatial distribution, Dwarf Rasbora prefers the Middle (Open Water) zone, whereas Japanese Ricefish (Medaka) occupies the Top (Surface) zone. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Japanese Ricefish (Medaka) is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

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. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–10 dGH. Regular testing will ensure conditions stay within this range.

To house Dwarf Rasbora and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 19 litres with a minimum length of 30 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Plants - Densely covered, Plants - Floating, Leaf Litter/Blackwater. 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.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Dwarf Rasbora and Japanese Ricefish (Medaka) need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.