Can Colombian Shark Catfish (Brackish) and Rhomb Barb Live Together?

Colombian Shark Catfish (Brackish) is a moderately assertive species (5/10), while Rhomb Barb is peaceful (2/10). This modest difference means Colombian Shark Catfish (Brackish) may occasionally assert dominance over Rhomb Barb.

Colombian Shark Catfish (Brackish) and Rhomb Barb 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.

The safe temperature window for both species falls between 23°C and 28°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

The pH requirements of Colombian Shark Catfish (Brackish) (7.5–8.5) and Rhomb Barb (5–7) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Colombian Shark Catfish (Brackish) needs 12–30 dGH while Rhomb Barb requires 1–10 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 Colombian Shark Catfish (Brackish) and Rhomb Barb 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), Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Densely covered. Meeting these requirements will help both species thrive.

Colombian Shark Catfish (Brackish) prefers High (River/Stream) flow while Rhomb Barb 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 Rhomb Barb 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.