Can Electric Blue Johannii and Freshwater Shark (Wallago) Live Together?

Electric Blue Johannii is a semi-aggressive species (8/10), while Freshwater Shark (Wallago) is highly aggressive (10/10). This modest difference means Freshwater Shark (Wallago) may occasionally assert dominance over Electric Blue Johannii.

Both Electric Blue Johannii and Freshwater Shark (Wallago) are highly aggressive, increasing the risk of violent confrontations.

Electric Blue Johannii and Freshwater Shark (Wallago) 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: Two aggressive species housed together increases risk of fighting.

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 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

The pH requirements of Electric Blue Johannii (7.8–8.6) and Freshwater Shark (Wallago) (6–7.6) 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 Electric Blue Johannii and Freshwater Shark (Wallago) 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), Established Algae (Otocinclus), 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.

Electric Blue Johannii and Freshwater Shark (Wallago) 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.