Can Colombian Shark Catfish (Brackish) and Marbled Hatchetfish Live Together?

Colombian Shark Catfish (Brackish) is a moderately assertive species (5/10), while Marbled Hatchetfish is peaceful (1/10). This notable difference means Colombian Shark Catfish (Brackish) may occasionally assert dominance over Marbled Hatchetfish.

In terms of spatial distribution, Colombian Shark Catfish (Brackish) prefers the Middle (Open Water) and Bottom (Substrate) zones, whereas Marbled Hatchetfish occupies the Top (Surface) zone. 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: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Marbled Hatchetfish 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.

Both fish can tolerate a pH between 7.5 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 12–12 dGH. Regular testing will ensure conditions stay within this range.

Crucially, these species require different water types — one needs freshwater while the other requires brackish conditions. This is a hard barrier to keeping them together.

To house Colombian Shark Catfish (Brackish) and Marbled Hatchetfish together, plan for an aquarium of at least 380 litres with a minimum length of 150 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), Plants - Floating, Leaf Litter/Blackwater. Meeting these requirements will help both species thrive.

Colombian Shark Catfish (Brackish) prefers High (River/Stream) flow while Marbled Hatchetfish needs Low (Still Water) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

Colombian Shark Catfish (Brackish) and Marbled Hatchetfish 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.