Can Molly (Sailfin/Black/Dalmatian) and Rummy-Nose Tetra Live Together?

Molly (Sailfin/Black/Dalmatian) is a generally mild-mannered species (3/10), while Rummy-Nose Tetra is peaceful (1/10). This modest difference means Molly (Sailfin/Black/Dalmatian) may occasionally assert dominance over Rummy-Nose Tetra.

Molly (Sailfin/Black/Dalmatian) and Rummy-Nose Tetra 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.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

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 Molly (Sailfin/Black/Dalmatian) (7.5–8.5) and Rummy-Nose Tetra (5.5–7) 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 Molly (Sailfin/Black/Dalmatian) and Rummy-Nose Tetra together, plan for an aquarium of at least 75 litres with a minimum length of 75 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: Plants - Densely covered, Established Algae (Otocinclus), Plants - lighly covered, Leaf Litter/Blackwater. 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.

Molly (Sailfin/Black/Dalmatian) and Rummy-Nose Tetra 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.

Feeding time deserves special attention with this pairing. Molly (Sailfin/Black/Dalmatian) is an aggressive eater that may prevent Rummy-Nose Tetra from getting enough food.

Because Molly (Sailfin/Black/Dalmatian) is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Rummy-Nose Tetra receives an adequate share.