Can Jack Dempsey and Largereye Lampeye Killifish Live Together?

Jack Dempsey is a semi-aggressive species (8/10), while Largereye Lampeye Killifish is peaceful (1/10). This notable difference means Jack Dempsey may occasionally assert dominance over Largereye Lampeye Killifish.

Large aggression gap (7 points) between Jack Dempsey and Largereye Lampeye Killifish increases stress risk for the more peaceful fish.

Jack Dempsey and Largereye Lampeye Killifish 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 Piscivore (Eats small/nano fish) behaviour of one fish directly conflicts with the Nano / Bite-sized (Predation Risk) trait of the other — piscivorous fish will prey on nano-sized tank mates..

Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species.

Worth noting: Largereye Lampeye Killifish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 22°C and 28°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 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 5–15 dGH. Regular testing will ensure conditions stay within this range.

To house Jack Dempsey and Largereye Lampeye Killifish together, plan for an aquarium of at least 200 litres with a minimum length of 120 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.

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: Sand (Sifters), Driftwood (Digestion/Hiding), Smooth Gravel (Sensitive Barbels), Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Jack Dempsey is a plant destroyer, which conflicts with Largereye Lampeye Killifish'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.

Jack Dempsey and Largereye Lampeye Killifish are the kind of pair that can look acceptable in a shop but become a maintenance problem at home. The main risk is not a single number in the chart; it is the way incompatible behavior, water needs, or pressure on space compounds over time once both fish are established in the same tank.