Can Gardner's Killifish and Swordtail Live Together?

Both Gardner's Killifish and Swordtail are generally mild-mannered species with an aggression score of 4/10. Their matching temperaments mean neither fish is likely to dominate the other in a shared aquarium.

Gardner's Killifish and Swordtail both frequent the Top (Surface) and 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: Gardner's Killifish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 21°C and 26°C. Aim for the midpoint of this range (around 23.5°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.

Hardness requirements are incompatible: Gardner's Killifish needs 4–10 dGH while Swordtail requires 12–30 dGH. An aquarium test kit is recommended for monitoring.

To house Gardner's Killifish and Swordtail together, plan for an aquarium of at least 132 litres with a minimum length of 80 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: Plants - Densely covered, Plants - Floating, Plants - lighly covered. 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.