Can Freshwater Toadfish (Prehistoric Monster Fish) and Lyretail Killifish Live Together?

Freshwater Toadfish (Prehistoric Monster Fish) is a semi-aggressive species (7/10), while Lyretail Killifish is generally mild-mannered (3/10). This notable difference means Freshwater Toadfish (Prehistoric Monster Fish) may occasionally assert dominance over Lyretail Killifish.

In terms of spatial distribution, Freshwater Toadfish (Prehistoric Monster Fish) prefers the Bottom (Substrate) zone, whereas Lyretail Killifish occupies the Top (Surface) and Middle (Open Water) zones. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

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..

Worth noting: Freshwater Toadfish (Prehistoric Monster Fish) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Lyretail 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 6 and 7. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 4–10 dGH. Regular testing will ensure conditions stay within this range.

To house Freshwater Toadfish (Prehistoric Monster Fish) and Lyretail Killifish together, plan for an aquarium of at least 75 litres with a minimum length of 60 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), Leaf Litter/Blackwater, Plants - Densely covered, 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.

Freshwater Toadfish (Prehistoric Monster Fish) and Lyretail 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.