Can Molly (Sailfin/Black/Dalmatian) and Silver Arowana Live Together?

Molly (Sailfin/Black/Dalmatian) is a generally mild-mannered species (3/10), while Silver Arowana is moderately assertive (6/10). This modest difference means Silver Arowana may occasionally assert dominance over Molly (Sailfin/Black/Dalmatian).

Molly (Sailfin/Black/Dalmatian) and Silver Arowana both frequent the 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: Silver Arowana 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 Molly (Sailfin/Black/Dalmatian) and Silver Arowana to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations.

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 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 12–12 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Molly (Sailfin/Black/Dalmatian) and Silver Arowana together, plan for an aquarium of at least 1200 litres with a minimum length of 240 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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: Plants - Densely covered, Established Algae (Otocinclus), Smooth Gravel (Sensitive Barbels). 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.