Can Altum Angel and Arfak Rainbowfish Live Together?

Altum Angel is a moderately assertive species (5/10), while Arfak Rainbowfish is peaceful (2/10). This modest difference means Altum Angel may occasionally assert dominance over Arfak Rainbowfish.

Altum Angel and Arfak Rainbowfish 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.

Worth noting: Arfak Rainbowfish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 27°C and 28°C. Aim for the midpoint of this range (around 27.5°C) for optimal comfort.

The pH requirements of Altum Angel (4.5–6.5) and Arfak Rainbowfish (7–8) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 5–5 dGH. Regular testing will ensure conditions stay within this range.

To house Altum Angel and Arfak Rainbowfish together, plan for an aquarium of at least 400 litres with a minimum length of 120 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), Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Plants - Floating, Plants - lighly covered, Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Altum Angel prefers Low (Still Water) flow while Arfak Rainbowfish needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

Altum Angel and Arfak Rainbowfish 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.