Can Lorentz's Rainbowfish and Wels Catfish (European Catfish) Live Together?

Lorentz's Rainbowfish 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 Lorentz's Rainbowfish.

Large aggression gap (6 points) between Lorentz's Rainbowfish and Wels Catfish (European Catfish) increases stress risk for the more peaceful fish.

In terms of spatial distribution, Lorentz's Rainbowfish 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.

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

There is no temperature overlap between Lorentz's Rainbowfish (26–30°C) and Wels Catfish (European Catfish) (4–25°C). This fundamental mismatch makes long-term cohabitation impractical.

Both fish can tolerate a pH between 7.2 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 8–15 dGH. Regular testing will ensure conditions stay within this range.

To house Lorentz's Rainbowfish 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, Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Smooth Gravel (Sensitive Barbels). 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.

Lorentz's Rainbowfish 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.