Can Mountain Rainbowfish and Red Eye Tetra Live Together?

Mountain Rainbowfish is a peaceful species (2/10), while Red Eye Tetra is generally mild-mannered (3/10). This modest difference means Red Eye Tetra may occasionally assert dominance over Mountain Rainbowfish.

Mountain Rainbowfish and Red Eye Tetra both frequent the Top (Surface) and 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: Mountain Rainbowfish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 22°C and 24°C. Aim for the midpoint of this range (around 23.0°C) for optimal comfort.

Both fish can tolerate a pH between 7.4 and 8.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 8–20 dGH. Regular testing will ensure conditions stay within this range.

To house Mountain Rainbowfish and Red Eye Tetra together, plan for an aquarium of at least 110 litres with a minimum length of 90 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: Driftwood (Digestion/Hiding), Plants - Densely covered. 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.

Mountain Rainbowfish and Red Eye Tetra work best when the tank gives each fish enough room to use its preferred level of the aquarium and enough cover to avoid constant visual contact. The score matters, but the real-world success usually comes from matching their pace, keeping water stable, and resisting the urge to crowd the tank just because the pair looks safe on paper.