Can Clown Killifish and Red-Tail Catfish Live Together?

Clown Killifish is a peaceful species (2/10), while Red-Tail Catfish is semi-aggressive (7/10). This notable difference means Red-Tail Catfish may occasionally assert dominance over Clown Killifish.

In terms of spatial distribution, Clown Killifish prefers the Top (Surface) zone, whereas Red-Tail Catfish occupies the Bottom (Substrate) zone. 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 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..

Worth noting: Red-Tail Catfish is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Clown Killifish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 23°C and 27°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 3–8 dGH. Regular testing will ensure conditions stay within this range.

To house Clown Killifish and Red-Tail Catfish together, plan for an aquarium of at least 3800 litres with a minimum length of 300 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: Plants - Floating, Plants - Densely covered, Leaf Litter/Blackwater, Sand (Sifters), Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Red-Tail Catfish is a plant destroyer, which conflicts with Clown Killifish's requirement for live plants. Compromise where possible or prioritise the more critical need.

Both species do well with low (still water) water movement, so a standard filtration setup rated for the tank volume should suffice.

Clown Killifish and Red-Tail Catfish 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.