Can Black Pacu and Violet Goby (Dragon Goby) Live Together?

Black Pacu is a generally mild-mannered species (4/10), while Violet Goby (Dragon Goby) is peaceful (2/10). This modest difference means Black Pacu may occasionally assert dominance over Violet Goby (Dragon Goby).

Black Pacu and Violet Goby (Dragon Goby) 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: Hyperactive swimmers can stress shy, slow-moving species through constant motion. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

Worth noting: Violet Goby (Dragon Goby) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Black Pacu is a known jumper, so a tight-fitting lid is essential.

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 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 12–15 dGH. Regular testing will ensure conditions stay within this range.

Crucially, these species require different water types — one needs freshwater while the other requires brackish conditions. This is a hard barrier to keeping them together.

To house Black Pacu and Violet Goby (Dragon Goby) together, plan for an aquarium of at least 4560 litres with a minimum length of 300 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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: Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Sand (Sifters), Shells (Breeding/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.

Feeding time deserves special attention with this pairing. Black Pacu is an aggressive eater that may prevent Violet Goby (Dragon Goby) from getting enough food.

Because Black Pacu is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Violet Goby (Dragon Goby) receives an adequate share.