Can Amazon Leaf Fish and Northern Mountain Swordtail Live Together?

Amazon Leaf Fish is a peaceful species (2/10), while Northern Mountain Swordtail is generally mild-mannered (3/10). This modest difference means Northern Mountain Swordtail may occasionally assert dominance over Amazon Leaf Fish.

Amazon Leaf Fish 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.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Amazon Leaf Fish is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Northern Mountain Swordtail is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 23°C and 25°C. Aim for the midpoint of this range (around 24.0°C) for optimal comfort.

The pH requirements of Amazon Leaf Fish (5–6.8) and Northern Mountain Swordtail (7–8) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 8–8 dGH. Regular testing will ensure conditions stay within this range.

To house Amazon Leaf Fish and Northern Mountain Swordtail together, plan for an aquarium of at least 110 litres with a minimum length of 90 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: Leaf Litter/Blackwater, Plants - Densely covered, Driftwood (Digestion/Hiding), Plants - Floating. Meeting these requirements will help both species thrive.

Amazon Leaf Fish 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.

Amazon Leaf Fish 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.