Can Delicate Blue-Eye and Mountain Rainbowfish Live Together?

Delicate Blue-Eye is a peaceful species (1/10), while Mountain Rainbowfish is peaceful (2/10). This modest difference means Mountain Rainbowfish may occasionally assert dominance over Delicate Blue-Eye.

Delicate Blue-Eye and Mountain Rainbowfish 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: Delicate Blue-Eye is a known jumper, so a tight-fitting lid is essential.

There is no temperature overlap between Delicate Blue-Eye (25–32°C) and Mountain Rainbowfish (17–24°C). This fundamental mismatch makes long-term cohabitation impractical.

Both fish can tolerate a pH between 7.4 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 8–15 dGH. Regular testing will ensure conditions stay within this range.

To house Delicate Blue-Eye and Mountain Rainbowfish 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: Plants - Densely covered, Plants - Floating, Driftwood (Digestion/Hiding). 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.

Delicate Blue-Eye and Mountain Rainbowfish 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.