Can Altum Angel and Cairns Rainbowfish Live Together?

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

Altum Angel and Cairns 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: Cairns Rainbowfish is a known jumper, so a tight-fitting lid is essential.

There is no temperature overlap between Altum Angel (27–32°C) and Cairns Rainbowfish (20–26°C). This fundamental mismatch makes long-term cohabitation impractical.

Both fish can tolerate a pH between 6.5 and 6.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 2–5 dGH. Regular testing will ensure conditions stay within this range.

To house Altum Angel and Cairns 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, Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Altum Angel prefers Low (Still Water) flow while Cairns 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 Cairns 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.