Can Clown Knifefish and Red-Tail Catfish Live Together?

Both Clown Knifefish and Red-Tail Catfish are semi-aggressive species with an aggression score of 7/10. Their matching temperaments mean neither fish is likely to dominate the other in a shared aquarium.

Both Clown Knifefish and Red-Tail Catfish are highly aggressive, increasing the risk of violent confrontations.

Clown Knifefish and Red-Tail Catfish both frequent the Bottom (Substrate) 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: Clown Knifefish is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Clown Knifefish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 6 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. An aquarium test kit is recommended for monitoring.

To house Clown Knifefish and Red-Tail Catfish together, plan for an aquarium of at least 4560 litres with a minimum length of 300 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Plants - Densely covered, Sand (Sifters). 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 Knifefish'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.