Can Betta Macrostoma and Colombian Shark Catfish (Brackish) Live Together?

Betta Macrostoma is a moderately assertive species (6/10), while Colombian Shark Catfish (Brackish) is moderately assertive (5/10). This modest difference means Betta Macrostoma may occasionally assert dominance over Colombian Shark Catfish (Brackish).

Betta Macrostoma and Colombian Shark Catfish (Brackish) 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: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Betta Macrostoma is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 22°C and 25°C. Aim for the midpoint of this range (around 23.5°C) for optimal comfort.

The pH requirements of Betta Macrostoma (4–6) and Colombian Shark Catfish (Brackish) (7.5–8.5) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Betta Macrostoma needs 0–5 dGH while Colombian Shark Catfish (Brackish) requires 12–30 dGH.

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 Betta Macrostoma and Colombian Shark Catfish (Brackish) 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: Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Floating, Sand (Sifters). Meeting these requirements will help both species thrive.

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

Betta Macrostoma and Colombian Shark Catfish (Brackish) 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.