Can Apistogramma viejita and Christmas Fulu Live Together?

Apistogramma viejita is a moderately assertive species (5/10), while Christmas Fulu is moderately assertive (6/10). This modest difference means Christmas Fulu may occasionally assert dominance over Apistogramma viejita.

Apistogramma viejita and Christmas Fulu both frequent the Bottom (Substrate) 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. Two territorial species may clash over territory, especially in smaller tanks.

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 Christmas Fulu (7.5–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Apistogramma viejita needs 1–8 dGH while Christmas Fulu requires 10–20 dGH.

To house Apistogramma viejita and Christmas Fulu 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: Sand (Sifters), Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), 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 Christmas Fulu 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.