Can Black Marble Hoplo and Japanese Ricefish (Medaka) Live Together?

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

In terms of spatial distribution, Black Marble Hoplo prefers the Bottom (Substrate) and Middle (Open Water) 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: Black Marble Hoplo is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 18°C and 28°C. Aim for the midpoint of this range (around 23.0°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 Black Marble Hoplo and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 115 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), Smooth Gravel (Sensitive Barbels), Plants - Densely covered, Plants - Floating. 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.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Black Marble Hoplo 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. Black Marble Hoplo is a known shrimp eater and may prey on small invertebrates or nano fish like Japanese Ricefish (Medaka).