Can Japanese Ricefish (Medaka) and Red Phantom Tetra Live Together?

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

In terms of spatial distribution, Japanese Ricefish (Medaka) prefers the Top (Surface) zone, whereas Red Phantom Tetra occupies the Middle (Open Water) 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 20°C and 24°C. Aim for the midpoint of this range (around 22.0°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 5–10 dGH. Regular testing will ensure conditions stay within this range.

To house Japanese Ricefish (Medaka) and Red Phantom Tetra together, plan for an aquarium of at least 60 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.

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. Japanese Ricefish (Medaka) and Red Phantom Tetra 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.