Can Mosquitofish (Gambusia) and Walking Catfish (Clarias) Live Together?

Mosquitofish (Gambusia) is a semi-aggressive species (7/10), while Walking Catfish (Clarias) is semi-aggressive (8/10). This modest difference means Walking Catfish (Clarias) may occasionally assert dominance over Mosquitofish (Gambusia).

Both Mosquitofish (Gambusia) and Walking Catfish (Clarias) are highly aggressive, increasing the risk of violent confrontations.

In terms of spatial distribution, Mosquitofish (Gambusia) prefers the Top (Surface) and Middle (Open Water) zones, whereas Walking Catfish (Clarias) 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.

Additional behavioural considerations to keep in mind: Two aggressive species housed together increases risk of fighting.

Worth noting: Walking Catfish (Clarias) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Walking Catfish (Clarias) is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat. Keep fin nippers in larger groups to distribute nipping behaviour among conspecifics rather than tank mates.

The safe temperature window for both species falls between 20°C and 28°C. Aim for the midpoint of this range (around 24.0°C) for optimal comfort.

Both fish can tolerate a pH between 6 and 8. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–20 dGH. Regular testing will ensure conditions stay within this range.

To house Mosquitofish (Gambusia) and Walking Catfish (Clarias) together, plan for an aquarium of at least 750 litres with a minimum length of 180 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.

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

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

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Mosquitofish (Gambusia) and Walking Catfish (Clarias) need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.