Can Cardinal Tetra and Pseudotropheus sp. Kingsizei Live Together?

Cardinal Tetra is a peaceful species (1/10), while Pseudotropheus sp. Kingsizei is semi-aggressive (8/10). This notable difference means Pseudotropheus sp. Kingsizei may occasionally assert dominance over Cardinal Tetra.

Large aggression gap (7 points) between Cardinal Tetra and Pseudotropheus sp. Kingsizei increases stress risk for the more peaceful fish.

Cardinal Tetra and Pseudotropheus sp. Kingsizei 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: Aggressive fish may bully and stress shy, slow-moving species. 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 Pseudotropheus sp. Kingsizei (7.5–8.5) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Cardinal Tetra needs 1–8 dGH while Pseudotropheus sp. Kingsizei requires 10–25 dGH.

To house Cardinal Tetra and Pseudotropheus sp. Kingsizei together, plan for an aquarium of at least 252 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: Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Densely covered, Sand (Sifters), Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Pseudotropheus sp. Kingsizei is a plant destroyer, which conflicts with Cardinal Tetra's requirement for live plants. Compromise where possible or prioritise the more critical need.

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 Pseudotropheus sp. Kingsizei 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.