Can Bucktooth Tetra (Exodon) and Red-Bellied Piranha Live Together?

Bucktooth Tetra (Exodon) is a highly aggressive species (9/10), while Red-Bellied Piranha is semi-aggressive (8/10). This modest difference means Bucktooth Tetra (Exodon) may occasionally assert dominance over Red-Bellied Piranha.

Both Bucktooth Tetra (Exodon) and Red-Bellied Piranha are highly aggressive, increasing the risk of violent confrontations.

Bucktooth Tetra (Exodon) and Red-Bellied Piranha 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.

There is a critical concern: the Eye Biter (Attacks slow moving fish) behaviour of one fish directly conflicts with the Shy / Slow Moving (Easily Stressed) trait of the other — eye biters attack slow-moving fish, risking permanent injury..

Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species. Hyperactive swimmers can stress shy, slow-moving species through constant motion. Two aggressive species housed together increases risk of fighting.

Worth noting: Bucktooth Tetra (Exodon) is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 6 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 4–15 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Bucktooth Tetra (Exodon) and Red-Bellied Piranha together, plan for an aquarium of at least 456 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: Driftwood (Digestion/Hiding), Plants - Floating. Meeting these requirements will help both species thrive.

Both species do well with moderate (standard) water movement, so a standard filtration setup rated for the tank volume should suffice.