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

Festivum is a generally mild-mannered species (4/10), while Molly (Sailfin/Black/Dalmatian) is generally mild-mannered (3/10). This modest difference means Festivum may occasionally assert dominance over Molly (Sailfin/Black/Dalmatian).

Festivum and Molly (Sailfin/Black/Dalmatian) both frequent the Top (Surface) and 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: Festivum is a known jumper, so a tight-fitting lid is essential.

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.

The pH requirements of Festivum (5.5–7.2) and Molly (Sailfin/Black/Dalmatian) (7.5–8.5) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 12–12 dGH. Regular testing will ensure conditions stay within this range.

To house Festivum and Molly (Sailfin/Black/Dalmatian) together, plan for an aquarium of at least 150 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: Driftwood (Digestion/Hiding), Plants - Floating, Plants - Densely covered, Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Festivum is a plant destroyer, which conflicts with Molly (Sailfin/Black/Dalmatian)'s requirement for live plants. Compromise where possible or prioritise the more critical need.

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

Festivum and Molly (Sailfin/Black/Dalmatian) 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.