Can Rachov's Killifish (Annual) and Red-Bellied Piranha Live Together?

Rachov's Killifish (Annual) is a generally mild-mannered species (3/10), while Red-Bellied Piranha is semi-aggressive (8/10). This notable difference means Red-Bellied Piranha may occasionally assert dominance over Rachov's Killifish (Annual).

Rachov's Killifish (Annual) and Red-Bellied Piranha both frequent the Middle (Open Water) and Bottom (Substrate) 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 Nano / Bite-sized (Predation Risk) behaviour of one fish directly conflicts with the Piscivore (Eats small/nano fish) trait of the other — piscivorous fish will prey on nano-sized tank mates..

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Rachov's Killifish (Annual) is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 26°C. Aim for the midpoint of this range (around 25.0°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 4–12 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Rachov's Killifish (Annual) 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: Soil / Nutrient Rich, Leaf Litter/Blackwater, Plants - Densely covered, Driftwood (Digestion/Hiding), 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.