Can Flowerhorn Cichlid and Northern Mountain Swordtail Live Together?

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

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

Flowerhorn Cichlid and Northern Mountain Swordtail 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: Northern Mountain Swordtail is a known jumper, so a tight-fitting lid is essential.

There is no temperature overlap between Flowerhorn Cichlid (26–30°C) and Northern Mountain Swordtail (20–25°C). This fundamental mismatch makes long-term cohabitation impractical.

Both fish can tolerate a pH between 7.4 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 9–20 dGH. Regular testing will ensure conditions stay within this range.

To house Flowerhorn Cichlid and Northern Mountain Swordtail together, plan for an aquarium of at least 280 litres with a minimum length of 120 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), Smooth Gravel (Sensitive Barbels), Plants - Densely covered. Meeting these requirements will help both species thrive.

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

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

Flowerhorn Cichlid and Northern Mountain Swordtail 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.