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

Apistogramma viejita is a moderately assertive species (5/10), while Molly (Sailfin/Black/Dalmatian) is generally mild-mannered (3/10). This modest difference means Apistogramma viejita may occasionally assert dominance over Molly (Sailfin/Black/Dalmatian).

In terms of spatial distribution, Apistogramma viejita prefers the Bottom (Substrate) zone, whereas Molly (Sailfin/Black/Dalmatian) 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.

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 Apistogramma viejita (5–7) and Molly (Sailfin/Black/Dalmatian) (7.5–8.5) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Apistogramma viejita needs 1–8 dGH while Molly (Sailfin/Black/Dalmatian) requires 12–30 dGH.

To house Apistogramma viejita and Molly (Sailfin/Black/Dalmatian) together, plan for an aquarium of at least 75 litres with a minimum length of 60 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), Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Densely covered, Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

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

Apistogramma viejita 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.

Feeding time deserves special attention with this pairing. Molly (Sailfin/Black/Dalmatian) is an aggressive eater that may prevent Apistogramma viejita 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 Apistogramma viejita receives an adequate share.