Can Japanese Ricefish (Medaka) and Silver Arowana Live Together?
Japanese Ricefish (Medaka) and Silver Arowana are not recommended as tank mates due to piscivorous fish will prey on nano-sized tank mates.. Housing these species together is likely to result in stress, health problems, or direct harm to one or both fish.
At a Glance
Behaviour & Temperament
Japanese Ricefish (Medaka) is a peaceful species (2/10), while Silver Arowana is moderately assertive (6/10). This notable difference means Silver Arowana may occasionally assert dominance over Japanese Ricefish (Medaka).
Japanese Ricefish (Medaka) and Silver Arowana 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.
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..
Worth noting: Japanese Ricefish (Medaka) is a known jumper, so a tight-fitting lid is essential.
Water Parameters
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 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 5–12 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.
Tank Setup
To house Japanese Ricefish (Medaka) and Silver Arowana together, plan for an aquarium of at least 1200 litres with a minimum length of 240 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, Smooth Gravel (Sensitive Barbels). 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.
Find the right tank equipment
Browse tanks, décor, and equipment suited for this setup.
Frequently Asked Questions
Can Japanese Ricefish (Medaka) and Silver Arowana live together?▾
No. This combination is not recommended. Key incompatibilities — such as critical behavioural conflicts — make cohabitation unsafe.
What size tank do Japanese Ricefish (Medaka) and Silver Arowana need?▾
A minimum of 1200 litres (tank length at least 240 cm) is recommended. This provides enough space for both species to establish their own areas and reduces the likelihood of territorial disputes.
What water temperature is best for Japanese Ricefish (Medaka) and Silver Arowana together?▾
Keep the aquarium between 24°C and 28°C. A target of around 26.0°C sits comfortably within both species' preferred ranges.
Are Japanese Ricefish (Medaka) or Silver Arowana aggressive?▾
Japanese Ricefish (Medaka) is peaceful (2/10) and Silver Arowana is moderately assertive (6/10). The gap in aggression levels means the calmer fish may experience stress from the more assertive one.
What pH do Japanese Ricefish (Medaka) and Silver Arowana need?▾
Both species overlap in the 6.5–7.5 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.
How do I manage Silver Arowana's territorial behaviour?▾
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Silver Arowana space to claim a territory without encroaching on the other fish's area. Adding décor that divides the tank into distinct zones works especially well.
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