Can Cairns Rainbowfish and Fuelleborn's Cichlid Live Together?

Cairns Rainbowfish is a peaceful species (2/10), while Fuelleborn's Cichlid is semi-aggressive (8/10). This notable difference means Fuelleborn's Cichlid may occasionally assert dominance over Cairns Rainbowfish.

Large aggression gap (6 points) between Cairns Rainbowfish and Fuelleborn's Cichlid increases stress risk for the more peaceful fish.

Cairns Rainbowfish and Fuelleborn's Cichlid 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.

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

The safe temperature window for both species falls between 24°C and 26°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

The pH requirements of Cairns Rainbowfish (6.5–7.6) and Fuelleborn's Cichlid (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 10–10 dGH. Regular testing will ensure conditions stay within this range.

To house Cairns Rainbowfish and Fuelleborn's Cichlid together, plan for an aquarium of at least 274 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: Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Sand (Sifters), Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

Both species do well with high (river/stream) water movement, so a standard filtration setup rated for the tank volume should suffice.

Cairns Rainbowfish and Fuelleborn's Cichlid 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.