Can Green Neon Tetra and Vieja fenestrata Live Together?

Green Neon Tetra is a peaceful species (0/10), while Vieja fenestrata is semi-aggressive (8/10). This notable difference means Vieja fenestrata may occasionally assert dominance over Green Neon Tetra.

Large aggression gap (8 points) between Green Neon Tetra and Vieja fenestrata increases stress risk for the more peaceful fish.

Green Neon Tetra and Vieja fenestrata 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.

The safe temperature window for both species falls between 24°C and 29°C. Aim for the midpoint of this range (around 26.5°C) for optimal comfort.

The pH requirements of Green Neon Tetra (4.5–6.5) and Vieja fenestrata (7–8) do not overlap, making it impossible to satisfy both species simultaneously.

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

To house Green Neon Tetra and Vieja fenestrata 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, Plants - Densely covered, Plants - Floating, Sand (Sifters), Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Vieja fenestrata is a plant destroyer, which conflicts with Green Neon 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.

Green Neon Tetra and Vieja fenestrata 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.