Can Gardner's Killifish and Molly (Sailfin/Black/Dalmatian) Live Together?

Gardner's Killifish is a generally mild-mannered species (4/10), while Molly (Sailfin/Black/Dalmatian) is generally mild-mannered (3/10). This modest difference means Gardner's Killifish may occasionally assert dominance over Molly (Sailfin/Black/Dalmatian).

Gardner's Killifish and Molly (Sailfin/Black/Dalmatian) 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 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 7.5 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 Molly (Sailfin/Black/Dalmatian) requires 12–30 dGH. An aquarium test kit is recommended for monitoring.

To house Gardner's Killifish and Molly (Sailfin/Black/Dalmatian) together, plan for an aquarium of at least 90 litres with a minimum length of 60 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, Established Algae (Otocinclus). 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.