Can Boeseman's Rainbowfish and Cardinal Tetra Live Together?

Boeseman's Rainbowfish is a peaceful species (2/10), while Cardinal Tetra is peaceful (1/10). This modest difference means Boeseman's Rainbowfish may occasionally assert dominance over Cardinal Tetra.

Boeseman's Rainbowfish and Cardinal Tetra 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.

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

The safe temperature window for both species falls between 26°C and 29°C. Aim for the midpoint of this range (around 27.5°C) for optimal comfort.

Both fish can tolerate a pH between 7 and 7. Maintaining a stable value within this band is more important than hitting an exact number.

Hardness requirements are incompatible: Boeseman's Rainbowfish needs 9–19 dGH while Cardinal Tetra requires 1–8 dGH. An aquarium test kit is recommended for monitoring.

To house Boeseman's Rainbowfish and Cardinal Tetra together, plan for an aquarium of at least 240 litres with a minimum length of 120 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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: Plants - lighly covered, Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Densely covered. Meeting these requirements will help both species thrive.

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

Feeding time deserves special attention with this pairing. Boeseman's Rainbowfish is an aggressive eater that may prevent Cardinal Tetra from getting enough food.

Because Boeseman's Rainbowfish 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.