Can Black Pacu and Boeseman's Rainbowfish Live Together?

Black Pacu is a generally mild-mannered species (4/10), while Boeseman's Rainbowfish is peaceful (2/10). This modest difference means Black Pacu may occasionally assert dominance over Boeseman's Rainbowfish.

Black Pacu and Boeseman's Rainbowfish both frequent the Middle (Open Water) 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: Black Pacu is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 26°C and 28°C. Aim for the midpoint of this range (around 27.0°C) for optimal comfort.

Both fish can tolerate a pH between 7 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 9–15 dGH. Regular testing will ensure conditions stay within this range.

To house Black Pacu and Boeseman's Rainbowfish together, plan for an aquarium of at least 4560 litres with a minimum length of 300 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: Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Plants - lighly covered. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Black Pacu is a plant destroyer, which conflicts with Boeseman's Rainbowfish'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.