Can Alligator Gar and Colombian Shark Catfish (Brackish) Live Together?

Alligator Gar is a semi-aggressive species (7/10), while Colombian Shark Catfish (Brackish) is moderately assertive (5/10). This modest difference means Alligator Gar may occasionally assert dominance over Colombian Shark Catfish (Brackish).

Alligator Gar and Colombian Shark Catfish (Brackish) both frequent the Middle (Open Water) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.

Worth noting: Alligator Gar is a known jumper, so a tight-fitting lid is essential.

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. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 12–25 dGH. Regular testing will ensure conditions stay within this range.

To house Alligator Gar and Colombian Shark Catfish (Brackish) together, plan for an aquarium of at least 8000 litres with a minimum length of 400 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: Smooth Gravel (Sensitive Barbels), Sand (Sifters). 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.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Alligator Gar and Colombian Shark Catfish (Brackish) 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.