Can Black Ocellatus and X-Ray Tetra (Pristella) Live Together?

Black Ocellatus is a semi-aggressive species (7/10), while X-Ray Tetra (Pristella) is peaceful (1/10). This notable difference means Black Ocellatus may occasionally assert dominance over X-Ray Tetra (Pristella).

Large aggression gap (6 points) between Black Ocellatus and X-Ray Tetra (Pristella) increases stress risk for the more peaceful fish.

Black Ocellatus and X-Ray Tetra (Pristella) both frequent the Bottom (Substrate) 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: Shrimp eaters may also prey on very small nano fish.

To improve the chances of a peaceful coexistence in this community tank: Provide a significantly larger tank (at least 50% more volume than the minimum) to allow both Black Ocellatus and X-Ray Tetra (Pristella) to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations. A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

The safe temperature window for both species falls between 23°C and 28°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 and 8. 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 Black Ocellatus and X-Ray Tetra (Pristella) together, plan for an aquarium of at least 60 litres with a minimum length of 60 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: Sand (Sifters), Shells (Breeding/Hiding), Plants - Densely covered. Meeting these requirements will help both species thrive.

Both species do well with low (still water) 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. Black Ocellatus and X-Ray Tetra (Pristella) 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.

Feeding time deserves special attention with this pairing. Black Ocellatus is a known shrimp eater and may prey on small invertebrates or nano fish like X-Ray Tetra (Pristella).