Can Leopoldi Stingray (Black Diamond) and Northern Mountain Swordtail Live Together?

Leopoldi Stingray (Black Diamond) is a moderately assertive species (5/10), while Northern Mountain Swordtail is generally mild-mannered (3/10). This modest difference means Leopoldi Stingray (Black Diamond) may occasionally assert dominance over Northern Mountain Swordtail.

In terms of spatial distribution, Leopoldi Stingray (Black Diamond) prefers the Bottom (Substrate) zone, whereas Northern Mountain Swordtail occupies the Top (Surface) and Middle (Open Water) zones. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

Worth noting: Northern Mountain Swordtail is a known jumper, so a tight-fitting lid is essential.

There is no temperature overlap between Leopoldi Stingray (Black Diamond) (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 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 8–10 dGH. Regular testing will ensure conditions stay within this range.

To house Leopoldi Stingray (Black Diamond) and Northern Mountain Swordtail together, plan for an aquarium of at least 1135 litres with a minimum length of 240 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.

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

Leopoldi Stingray (Black Diamond) 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.