Can African Lungfish and Northern Mountain Swordtail Live Together?

African Lungfish is a highly aggressive species (10/10), while Northern Mountain Swordtail is generally mild-mannered (3/10). This notable difference means African Lungfish may occasionally assert dominance over Northern Mountain Swordtail.

Large aggression gap (7 points) between African Lungfish and Northern Mountain Swordtail increases stress risk for the more peaceful fish.

African Lungfish and Northern Mountain Swordtail both frequent the Middle (Open Water) and Top (Surface) 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: African Lungfish is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: Provide a significantly larger tank (at least 50% more volume than the minimum) to allow both African Lungfish and Northern Mountain Swordtail to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations. A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

The safe temperature window for both species falls between 24°C and 25°C. Aim for the midpoint of this range (around 24.5°C) for optimal comfort.

Both fish can tolerate a pH between 7 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 8–20 dGH. Regular testing will ensure conditions stay within this range.

To house African Lungfish and Northern Mountain Swordtail together, plan for an aquarium of at least 680 litres with a minimum length of 180 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), Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Plants - Densely covered. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: African Lungfish is a plant destroyer, which conflicts with Northern Mountain Swordtail's requirement for live plants. Compromise where possible or prioritise the more critical need.

African Lungfish prefers Low (Still Water) flow while Northern Mountain Swordtail needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.