Can Red Tailed Black Shark and True Julii Corydoras Live Together?

Red Tailed Black Shark is a semi-aggressive species (7/10), while True Julii Corydoras is peaceful (0/10). This notable difference means Red Tailed Black Shark may occasionally assert dominance over True Julii Corydoras.

Large aggression gap (7 points) between Red Tailed Black Shark and True Julii Corydoras increases stress risk for the more peaceful fish.

Red Tailed Black Shark and True Julii Corydoras 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.

Worth noting: Red Tailed Black Shark is a known jumper, so a tight-fitting lid is essential.

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 Red Tailed Black Shark and True Julii Corydoras 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 26°C. Aim for the midpoint of this range (around 24.5°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 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 5–15 dGH. Regular testing will ensure conditions stay within this range.

To house Red Tailed Black Shark and True Julii Corydoras together, plan for an aquarium of at least 208 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: Driftwood (Digestion/Hiding), Plants - Densely covered, Smooth Gravel (Sensitive Barbels), Sand (Sifters). 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.