Can Japanese Ricefish (Medaka) and Pacific Sturgeon Live Together?

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

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

There is a critical concern: the Nano / Bite-sized (Predation Risk) behaviour of one fish directly conflicts with the Piscivore (Eats small/nano fish) trait of the other — piscivorous fish will prey on nano-sized tank mates..

Additional behavioural considerations to keep in mind: Shrimp eaters may also prey on very small nano fish.

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 10°C and 22°C. Aim for the midpoint of this range (around 16.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 and 8. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–20 dGH. Regular testing will ensure conditions stay within this range.

To house Japanese Ricefish (Medaka) and Pacific Sturgeon together, plan for an aquarium of at least 20000 litres with a minimum length of 600 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: Plants - Densely covered, Plants - Floating, Sand (Sifters), Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Japanese Ricefish (Medaka) prefers Low (Still Water) flow while Pacific Sturgeon needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

Japanese Ricefish (Medaka) and Pacific Sturgeon 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.

Feeding time deserves special attention with this pairing. Pacific Sturgeon is a known shrimp eater and may prey on small invertebrates or nano fish like Japanese Ricefish (Medaka).

Because Pacific Sturgeon is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Japanese Ricefish (Medaka) receives an adequate share.