Can Cardinal Tetra and Scat (Brackish) Live Together?

Cardinal Tetra is a peaceful species (1/10), while Scat (Brackish) is generally mild-mannered (4/10). This modest difference means Scat (Brackish) may occasionally assert dominance over Cardinal Tetra.

Cardinal Tetra and Scat (Brackish) 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. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

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 Scat (Brackish) (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 Scat (Brackish) requires 12–30 dGH.

Crucially, these species require different water types — one needs freshwater while the other requires brackish conditions. This is a hard barrier to keeping them together.

To house Cardinal Tetra and Scat (Brackish) together, plan for an aquarium of at least 450 litres with a minimum length of 150 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), Smooth Gravel (Sensitive Barbels), Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

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

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

Cardinal Tetra and Scat (Brackish) 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.

Feeding time deserves special attention with this pairing. Scat (Brackish) is an aggressive eater that may prevent Cardinal Tetra from getting enough food.

Because Scat (Brackish) is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Cardinal Tetra receives an adequate share.