Can Goldfish (Comet / Common) and Japanese Ricefish (Medaka) Live Together?
Yes, Goldfish (Comet / Common) and Japanese Ricefish (Medaka) are ideal tank mates. Both species share compatible water parameters and peaceful temperaments, making them well-suited for a community aquarium. A minimum tank size of 240 litres is recommended.
At a Glance
Behaviour & Temperament
Goldfish (Comet / Common) 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 Goldfish (Comet / Common).
Goldfish (Comet / Common) and Japanese Ricefish (Medaka) 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.
Water Parameters
The safe temperature window for both species falls between 10°C and 24°C. Aim for the midpoint of this range (around 17.0°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. An aquarium test kit is recommended for monitoring.
Tank Setup
To house Goldfish (Comet / Common) and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 240 litres with a minimum length of 120 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: Sand (Sifters), Smooth Gravel (Sensitive Barbels), Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.
Note a potential conflict in setup requirements: Goldfish (Comet / Common) is a plant destroyer, which conflicts with Japanese Ricefish (Medaka)'s requirement for live plants. Compromise where possible or prioritise the more critical need.
Both species do well with moderate (standard) water movement, so a standard filtration setup rated for the tank volume should suffice.
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Frequently Asked Questions
Can Goldfish (Comet / Common) and Japanese Ricefish (Medaka) live together?▾
Yes. Goldfish (Comet / Common) and Japanese Ricefish (Medaka) are considered ideal tank mates. Their water parameters, temperaments, and behaviour profiles are well matched for a community aquarium.
What size tank do Goldfish (Comet / Common) and Japanese Ricefish (Medaka) need?▾
A minimum of 240 litres (tank length at least 120 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 Goldfish (Comet / Common) and Japanese Ricefish (Medaka) together?▾
Keep the aquarium between 10°C and 24°C. A target of around 17.0°C sits comfortably within both species' preferred ranges.
Are Goldfish (Comet / Common) or Japanese Ricefish (Medaka) aggressive?▾
Goldfish (Comet / Common) is peaceful (1/10) and Japanese Ricefish (Medaka) is peaceful (2/10). Their similar temperaments generally lead to a peaceful coexistence.
What pH do Goldfish (Comet / Common) and Japanese Ricefish (Medaka) need?▾
Both species overlap in the 6.5–8 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.
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