Can Cardinal Tetra and Fosso Cichlid (Fossorochromis rostratus) Live Together?

Cardinal Tetra is a peaceful species (1/10), while Fosso Cichlid (Fossorochromis rostratus) is moderately assertive (6/10). This notable difference means Fosso Cichlid (Fossorochromis rostratus) may occasionally assert dominance over Cardinal Tetra.

Cardinal Tetra and Fosso Cichlid (Fossorochromis rostratus) 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.

There is a critical concern: the Nano / Bite-sized (Predation Risk) behaviour of one fish directly conflicts with the Piscivore (Eats small/nano fish) trait of the other — piscivorous fish will prey on nano-sized tank mates..

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

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 Cardinal Tetra (4–7) and Fosso Cichlid (Fossorochromis rostratus) (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Cardinal Tetra needs 1–8 dGH while Fosso Cichlid (Fossorochromis rostratus) requires 10–25 dGH.

To house Cardinal Tetra and Fosso Cichlid (Fossorochromis rostratus) together, plan for an aquarium of at least 680 litres with a minimum length of 180 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: Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Densely covered, Sand (Sifters). 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.

Cardinal Tetra and Fosso Cichlid (Fossorochromis rostratus) 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.