Can Aequidens sp. Atabapo and Japanese Ricefish (Medaka) Live Together?

Aequidens sp. Atabapo is a moderately assertive species (6/10), while Japanese Ricefish (Medaka) is peaceful (2/10). This notable difference means Aequidens sp. Atabapo may occasionally assert dominance over Japanese Ricefish (Medaka).

In terms of spatial distribution, Aequidens sp. Atabapo 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.

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.

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 Aequidens sp. Atabapo 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.

The safe temperature window for both species falls between 25°C and 28°C. Aim for the midpoint of this range (around 26.5°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 and 7. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–8 dGH. Regular testing will ensure conditions stay within this range.

To house Aequidens sp. Atabapo and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 110 litres with a minimum length of 90 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: Sand (Sifters), Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Aequidens sp. Atabapo 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 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. Aequidens sp. Atabapo and Japanese Ricefish (Medaka) 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.

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