Can Colombian Shark Catfish (Brackish) and Sailfin Molly Live Together?

Colombian Shark Catfish (Brackish) is a moderately assertive species (5/10), while Sailfin Molly is generally mild-mannered (3/10). This modest difference means Colombian Shark Catfish (Brackish) may occasionally assert dominance over Sailfin Molly.

Colombian Shark Catfish (Brackish) and Sailfin Molly 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.

The safe temperature window for both species falls between 22°C and 28°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 and 8.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 15–30 dGH. Regular testing will ensure conditions stay within this range.

To house Colombian Shark Catfish (Brackish) and Sailfin Molly 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.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Sand (Sifters), Established Algae (Otocinclus), Plants - Densely covered. Meeting these requirements will help both species thrive.

Both species do well with high (river/stream) water movement, so a standard filtration setup rated for the tank volume should suffice.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Colombian Shark Catfish (Brackish) and Sailfin Molly need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.