Can Blackline Rasbora and Geophagus Orange Head Tapajos Live Together?

Blackline Rasbora is a peaceful species (1/10), while Geophagus Orange Head Tapajos is generally mild-mannered (3/10). This modest difference means Geophagus Orange Head Tapajos may occasionally assert dominance over Blackline Rasbora.

Blackline Rasbora and Geophagus Orange Head Tapajos 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.

Worth noting: Blackline Rasbora is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 26°C and 26°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 6 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 2–10 dGH. Regular testing will ensure conditions stay within this range.

To house Blackline Rasbora and Geophagus Orange Head Tapajos together, plan for an aquarium of at least 280 litres with a minimum length of 120 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Plants - Densely covered, Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Sand (Sifters), Smooth Gravel (Sensitive Barbels). 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.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Blackline Rasbora and Geophagus Orange Head Tapajos need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.