Can Gertrude's Spotted Blue-eye and Wels Catfish (European Catfish) Live Together?

Gertrude's Spotted Blue-eye is a peaceful species (2/10), while Wels Catfish (European Catfish) is semi-aggressive (8/10). This notable difference means Wels Catfish (European Catfish) may occasionally assert dominance over Gertrude's Spotted Blue-eye.

Large aggression gap (6 points) between Gertrude's Spotted Blue-eye and Wels Catfish (European Catfish) increases stress risk for the more peaceful fish.

In terms of spatial distribution, Gertrude's Spotted Blue-eye prefers the Top (Surface) and Middle (Open Water) zones, whereas Wels Catfish (European 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: Wels Catfish (European Catfish) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Gertrude's Spotted Blue-eye is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 21°C and 25°C. Aim for the midpoint of this range (around 23.0°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.

To house Gertrude's Spotted Blue-eye and Wels Catfish (European Catfish) together, plan for an aquarium of at least 10000 litres with a minimum length of 400 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 - Densely covered, Plants - Floating, Leaf Litter/Blackwater, Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding). 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.

Gertrude's Spotted Blue-eye and Wels Catfish (European 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.