Can Harlequin Shark and Trout Cichlid (Champsochromis) Live Together?

Harlequin Shark is a semi-aggressive species (8/10), while Trout Cichlid (Champsochromis) is semi-aggressive (7/10). This modest difference means Harlequin Shark may occasionally assert dominance over Trout Cichlid (Champsochromis).

Both Harlequin Shark and Trout Cichlid (Champsochromis) are highly aggressive, increasing the risk of violent confrontations.

In terms of spatial distribution, Harlequin Shark prefers the Bottom (Substrate) zone, whereas Trout Cichlid (Champsochromis) occupies the Top (Surface) and Middle (Open Water) zones. 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 territorial species may clash over territory, especially in smaller tanks.

Worth noting: Trout Cichlid (Champsochromis) is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 27°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

The pH requirements of Harlequin Shark (6–7.5) and Trout Cichlid (Champsochromis) (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 10–15 dGH. Regular testing will ensure conditions stay within this range.

To house Harlequin Shark and Trout Cichlid (Champsochromis) together, plan for an aquarium of at least 500 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.

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: Sand (Sifters), Driftwood (Digestion/Hiding), Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

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

Harlequin Shark and Trout Cichlid (Champsochromis) 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.