Can Scat (Brackish) and Threadfin Rainbowfish Live Together?

Scat (Brackish) is a generally mild-mannered species (4/10), while Threadfin Rainbowfish is peaceful (1/10). This modest difference means Scat (Brackish) may occasionally assert dominance over Threadfin Rainbowfish.

Scat (Brackish) and Threadfin Rainbowfish 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.

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: Threadfin Rainbowfish 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 12–12 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 Scat (Brackish) and Threadfin Rainbowfish 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: Sand (Sifters), Smooth Gravel (Sensitive Barbels), Established Algae (Otocinclus), Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Scat (Brackish) is a plant destroyer, which conflicts with Threadfin Rainbowfish's requirement for live plants. Compromise where possible or prioritise the more critical need.

Scat (Brackish) prefers High (River/Stream) flow while Threadfin Rainbowfish needs Low (Still Water) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

Scat (Brackish) and Threadfin Rainbowfish 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.

Feeding time deserves special attention with this pairing. Scat (Brackish) is an aggressive eater that may prevent Threadfin Rainbowfish from getting enough food.

Because Scat (Brackish) is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Threadfin Rainbowfish receives an adequate share.