Can Freshwater Shark (Wallago) and Masked Julie (Julidochromis) Live Together?

Freshwater Shark (Wallago) is a highly aggressive species (10/10), while Masked Julie (Julidochromis) is moderately assertive (6/10). This notable difference means Freshwater Shark (Wallago) may occasionally assert dominance over Masked Julie (Julidochromis).

Freshwater Shark (Wallago) and Masked Julie (Julidochromis) both frequent the Middle (Open Water) and 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.

Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species. Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Freshwater Shark (Wallago) is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 23°C and 27°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

The pH requirements of Freshwater Shark (Wallago) (6–7.6) and Masked Julie (Julidochromis) (8–9) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 10–20 dGH. Regular testing will ensure conditions stay within this range.

To house Freshwater Shark (Wallago) and Masked Julie (Julidochromis) together, plan for an aquarium of at least 5500 litres with a minimum length of 300 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), 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.

Freshwater Shark (Wallago) and Masked Julie (Julidochromis) 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.