Can Convict Cichlid and Japanese Ricefish (Medaka) Live Together?

Convict Cichlid is a semi-aggressive species (8/10), while Japanese Ricefish (Medaka) is peaceful (2/10). This notable difference means Convict Cichlid may occasionally assert dominance over Japanese Ricefish (Medaka).

Large aggression gap (6 points) between Convict Cichlid and Japanese Ricefish (Medaka) increases stress risk for the more peaceful fish.

In terms of spatial distribution, Convict Cichlid prefers the Middle (Open Water) and Bottom (Substrate) zones, 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.

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: Provide a significantly larger tank (at least 50% more volume than the minimum) to allow both Convict Cichlid and Japanese Ricefish (Medaka) to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations. A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat. Keep fin nippers in larger groups to distribute nipping behaviour among conspecifics rather than tank mates.

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

For general hardness, the shared comfort zone is 6–20 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Convict Cichlid and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 90 litres with a minimum length of 75 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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: Sand (Sifters), Driftwood (Digestion/Hiding), Smooth Gravel (Sensitive Barbels), Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Convict Cichlid 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.